Monday, September 30, 2013

What is to participate in a Platonic form?

To: Matthew M.
From: Geoffrey Klempner
Subject: What is it to participate in a Platonic form?
Date: 7th December 2010 12:11

Dear Matthew,

Thank you for your email of 27 November, with your essay for the University of London Greek Philosophy: Plato and the Presocratics module, in response to the question, 'Does Plato have an intelligible and consistent account of what it is to participate in a form?'

This is not a bad essay. The main problem, however, is that you raise various issues with Plato's various forms, among which is his account of participation. But the question specifically asked about participation. The examiner doesn't want you to offer a general survey of Plato's theory of forms and the various criticisms that might be made about it.

I can't stress strongly enough the importance of focusing on the question. In this case, the examiner has been very specific: Is Plato's account of what it is to participate in a form intelligible? and is his account consistent? Potentially, therefore, there are four answers to this question: That the account is intelligible and consistent; or neither intelligible nor consistent; or intelligible but inconsistent; or consistent but unintelligible. (However, we can discount the last, since I have no idea what being 'consistently unintelligible' would mean!)

Is Plato's account consistent? The implication here is that Plato says various things about forms and how things participate in them in his different dialogues, and that there is, or may be, a problem in making the various things he says consistent with one another. Here, besides mentioning the Timaeus and the Parmenides, you should have mentioned other key dialogues where the forms play a significant role, e.g., the Phaedo and the Republic (at the very least).

Obviously, I can't write the essay for you, but one of the major issues which bears on Plato's account of participation in the forms -- and which you don't mention at all -- is the role of the forms as objects which we seek knowledge of by means of engaging in the Socratic dialectic, that is to say, seeking definitions of things like virtue (Meno), justice (Republic) etc. Forms are meant, in some way, to account for the very possibility of philosophical analysis (as one would now say), whether we actually reach this end-point or not. Here, the crucial property, which you do mention, is the notion which Aristotle terms 'formal cause'.

I like your suggestion that 'forms are like blueprints', which takes much of the pressure off the third man argument deployed in the Parmenides. The point, however, of forms as 'formal causes' is not just that they are blueprints 'for' some human craftsman or super-human demiurge, but that they represent knowledge attained through the dialectic. To 'know the form' of justice is to know what it means to say that an action is just or unjust.

It is true, however, that forms appear to play more than one role and this is a potential source of inconsistency. If one is seeking to defend Plato on this score, the question is whether there is a 'core role', such as the one suggested above, which in some sense explains or accounts for the others. Consider the Phaedo. Human beings are immortal, Plato argues through the mouthpiece of Socrates, because we can know the forms, and this is possible only because what is essential to us is in some sense 'akin' to the forms. We are not just material beings but something more. (In the Phaedo, there is also an argument which quite specifically that a form, e.g. of equality must exist, otherwise we would be unable to make judgements about what is equal or unequal.)

You do raise the issue of which things have 'forms'. In the Parmenides, the older philosopher criticizes the young Socrates for not believing that there are forms of such things as mud, hair and dirt. 'When you get older, you will learn not to despise such things'. If Plato's account of participation is taken literally -- a thing is correctly described as 'F' if and only if it participates in the form F -- how can hair or mud fail to have a form? (There's a possible answer to that but I'll leave you to work it out for yourself.)

Is Plato's account intelligible? You state at one point that Platonic forms are what we would term 'universals'. Many philosophers (including Bertrand Russell in his 'Problems of Philosophy') have considered the notion of universals to be essential to accounting for the possibility of judgement. (According to Russell, we are 'acquainted' with sense data and with universals; these are the ultimate 'constituents' of judgments.) So one way of posing the question would be to ask, in what way forms do more work than universals? Assuming the idea of a universal to be intelligible, is it possible to understand the extra work that forms are meant to do?

The key idea is that forms serve as paradigms. This becomes especially important in the case of value judgements. You mention this in your essay. We can't make judgements about which of two objects is more 'beautiful' than the other unless we have knowledge of the form of beauty, which serves as the ultimate standard of what is beautiful or not beautiful. But how exactly is this meant to work?

As I said, you have not written a bad essay, and many of the points I make here are implicit in what you say. But you do need to be more sharply focused on the question.

All the best,


Accounting for the truth of 'Santa Claus does not exist'

To: Emelie G.
From: Geoffrey Klempner
Subject: Accounting for the truth of 'Santa Claus does not exist'
Date: 30th November 2010 14:42

Dear Emelie,

Thank you for your email of 20 November, with your essay for the University of London Logic module, in response to the question, 'Is there a satisfactory account of the truth of the sentence 'Santa Claus does not exist'?'

This is not a bad answer to the question. The main elements of a response are there. Treating 'exists' as a Fregean second-order concept which applies to first-order concepts (or what Russell terms a 'propositional function') enables us to rephrase the proposition, 'Santa Claus does not exist' more perspicuously as a negative existential statement. E.g:

A. not-((Ex)(x lives at the North Pole and x gives presents to children at Christmas))

In this simple translation I have ignored the implication that there is one and only one Santa Claus. So if you wanted to be more precise, the translation would be:

B. not-((Ex)(x lives at the North Pole and x gives presents to children at Christmas) and (y)(y lives at the North Pole and y gives presents to children at Christmas -> x=y)))

This negative existential statement is false if and only if there IS one and ONLY one object which satisfies the first-order predicate, '...lives at the North Pole and ... gives presents to children at Christmas' -- i.e. Bertrand Russell's analysis of definite descriptions.

OK, so what's wrong with that? Why isn't the problem solved?

For two reasons, which you, in effect, cover in your essay, although in both cases there is more work to be done.

As you state, as a matter of historical fact, we know that it is possible or even likely that the character 'Santa Claus' was an actual person, about whom various stories and legends arose. In which case, notwithstanding the fact that there is no-one who lives at the North Pole and gives presents to children at Christmas, Santa Claus does exist (or did). So B is not correct as a translation of 'Santa Claus does not exist'. It is possible that B is true, even though 'Santa Claus' is the name of a real historical person.

How to deal with this? I would argue that statements of the form, 'X exists' or 'X does not exist' can be vague and potentially misleading. It all depends on what you mean by 'Santa Claus'. This is an endemic problem with any attempt to 'define' a name in terms of a set of descriptions. Which descriptions do you use? My answer would be that it depends on the context. Given a suitable context, there's no problem. Misunderstandings don't arise, provided that you are prepared to state exactly what you take to be necessary and sufficient for the 'existence of Santa Claus'.

In addition to this, there is dispute amongst philosophers of language concerning the correct account of proper names. The fact that the name 'Santa Claus' traces back to an existing individual would be taken by Kripke (in 'Naming and Necessity') as sufficient for the falsity of 'Santa Claus does not exist', even if, as seems to be the case, all our beliefs about the entity in question are false. However, even Kripke would accept that there are putative names which do not trace back to any existing entity through a 'chain of communication', and so the only way to account for the truth of negative existential statements in these cases is in Fregean terms, as in B, above.

The second problem arises in relation to fictional discourse. Although Santa Claus is not considered to a character of fiction, you could have made the point that we make statements 'about' Santa Claus which are considered true and not false:

'Santa Claus wears a red costume'

'Santa Claus has a white beard'

'Santa Claus drives a sleigh drawn by reindeer'

and so on.

Strictly, on a Russellian analysis, all these statements are false, not true. The question is how we can emend the analysis to allow for what Evans terms, 'pretence'. Within the 'talking about Santa Claus' game, various statements about Santa Claus are true or false. Outside the game, they are all false, because he does not exist. So we can say, for example, 'Santa Claus has a white beard, but it is not really true that Santa Claus has a white beard.'

However, it wasn't clear from what you said, what you take to be Sainsbury's objection to Evans. It looks to me that the problem is the one I highlighted above, viz. that in the absence of additional information to provide a context, one don't know what exactly someone means to deny when they assert that, e.g. Santa Claus does not (really) exist.

I was very lucky to be able to attend Evans' lectures on reference when I was a graduate student at Oxford. He was a dynamo. The lectures were one of my most memorable experiences of my time there.

All the best,


The justification of inductive reasoning

To: Mark S.
From: Geoffrey Klempner
Subject: The justification of inductive reasoning
Date: 30th November 2010 13:24

Dear Mark,

Thank you for your email of 22 November, with your essay for the University of London BA Methodology module, in response to the question, 'What, if anything, can explain the rationality of reasoning according to inductive principles?'

In this very long (nearly 6700 words) essay, you have undertaken a wide-ranging evaluation of all or most of the significant responses to the problem of induction. Obviously, you could not do this in a one hour examination answer. However as in previous essays I accept that this has more than one purpose. The work you have done for this will provide adequate ammunition for a range of possible exam questions.

What would a good exam answer look like? When a question is as general as this, I think that you are entitled to state at the beginning that you will look at one or two arguments that you consider the strongest, after disposing of the others in as few words as possible.

As I read through the various responses: from Kant, Popper, Reichenbach and Salmon, Strawson and Edwards, Putnam, Van Cleeve and Papineau, my overriding impression was that each of these represented a 'solution' of a kind, not a dead end or an example of fallacious reasoning. Maybe that just shows something about my natural tendency towards eclecticism. However, there is something that you say right at the end of the essay which raises a warning flag for me: I suspect that you have been overly tough with these putative 'solutions' (to use a generic term which includes what you term vindication, validation, deflation, deflection and ad hominem retaliation!). You state: 'Frank Ramsey was probably correct when he wrote that asking for a justification of induction 'was to cry for the moon'.'

Why? Because 'we have no idea what the future holds'. It's that simple. The very next moment my G5 computer might turn into a fire-breathing dragon. I can't prove that it won't. But is that all Hume was saying?

As you state at the beginning of your essay, the point isn't just that inductive inference doesn't produce the same degree of certainty as deductive inference. Everyone accepts that. The point is that we believe, falsely, that performing inductive inferences is reasonable, and either that this can be shown to be the case, or that it is not necessary to show that this is the case.

So let's play a game of make-believe. One hypothesis would be that nature is not uniform. The little bit that we have observed appears to be uniform, but on a wider view (which we have not yet attained) it turns out that various degrees of chaos reign. The problem with this is that it is not the worst case scenario. As science continues on its way, the threat seems to recede. Indeed, there is always the possibility that we could discover that we inhabit an island of regularity in a chaotic universe (somewhat like Anaximander's cosmology of the Apeiron). But this is not the worst case scenario because things would be even worse for us if we were the playthings of a mischievous deity, who deliberately leads us down blind alleys.

I am going to assume that we do not and cannot prove that the worst case scenario doesn't hold, and see how the various solutions that you canvas fare:

1. Kant. Your example of the alien Connie who always reasons counter-inductively, and Randy who always spins a coin, miss their target here. Kant's argument in the Transcendental Analytic broadly seeks to establish that experience is only possible on the condition that induction is justified. If I can't validly perform induction, then there are no such things as spatio-temporal particulars. If there are no objects of my perception, then there is no 'I'. The mischievous deity cannot, logically, create a world where either Connie or Randy exist as self-conscious, experiencing subjects. To me, that's an impressive result. It doesn't go all the way (a point made by Strawson in 'The Bounds of Sense') but it constitutes at least a partial answer to Hume.

2. You say that Popper's 'conjecture and refutation' are insufficient as a basis for belief, and yet it is beliefs that are a necessary condition for action. Well, I'm going to define a mental state called schmeblief. In the absence of beliefs, we rely on schmebliefs. We boldly go where no-one has gone before. But do we? I guess you would say that if *any* theory is OK so long as it is falsifiable, not just OK to test and consider but OK to act upon, that would be very scary indeed. That's true, but testing is precisely what we do when we are unsure whether or not to act. The table looks a bit small for my G5, so I give it a bit of a wobble and a push and it feels solid enough. That's what I mean by schmeblief, and also what I think Popper is getting at with 'corroboration'.

3. Reichenbach's response seems rather similar in this respect. Life is a percentage-game, you can't always rely on playing a winner. 'Belief' is too clumsy a concept to capture this idea. My best bet is that the table will not collapse.

4. On Strawson's behalf, I would argue that it is part of what we mean by 'inductive grounds' that these grounds are defeasable. It is irrational to assume the existence of an mischievous deity, but of course we could be wrong. However, the rational thing to do is not assume the worst-case scenario, to do so would be paranoid.

5. I'm not sure whether it's OK to treat Putnam's argument for realism in science as an attempted justification of induction. It involves induction, to be sure, but it's aim is to combat scepticism about unobservables -- the view which motivates various anti-realist positions such as instrumentalism, fictionalism etc. Notwithstanding the observation that the history of science is a graveyard of discarded theories, surely it is still more rational to believe that our current theory is true than otherwise.

6. As a contextualist about knowledge, I'm not sure what to say about reliabilism, that hasn't been covered by the above. It has never occurred to me that a reliabilist would claim to have solved Hume's problem. We don't need internalist 'justification', the reliabilist will say. But it's still a valid question to ask what justification we *could* provide, if challenged.

All the best,


Refutation of egocentric subjectivism

To: Andrew A.
From: Geoffrey Klempner
Subject: Refutation of egocentric subjectivism
Date: 29th November 2010 13:01

Dear Andy,

Thank you for your email of 20 November, with your second essay for the Metaphysics program, in response to the question, 'Imagine that you are a former defender of egocentric subjectivism who has been persuaded to reject the theory. Apart from being convinced that the theory you once believed in is false, what is it that you now believe?'

You offer an elegant exposition of the arguments leading up to the rejection of egocentric subjectivism, including the 'transcendental' version of subjectivism which arises when Kant's second Refutation of Idealism is employed to correct the errors of 'naive' subjectivism. As you explain, you no longer believe that the world is ultimately made up of the material of your subjective awareness. There has to something that is not 'mine'. Or, as you put it, 'I understood that to seek to define reality was to seek to lay bare the illusions I held about my position in relation to the world. I could no longer place myself at the heart of the question because reality simply didn't begin with me. Neither could I set any store by an answer that pictured the raw subjective data of my world as the stuff of actuality.'

OK, so what is it that you now believe?

I feel this question keenly. The idea of metaphysics as a 'dialectic of illusion' is tempting precisely because it seems to dispense with any need to 'say what I believe'. Metaphysics isn't about beliefs. it is about rejecting illusions. -- That is, in fact, a thinly disguised version of the later Wittgenstein's view of philosophy in general. We are battling against the 'bewitchment of the understanding', seeking to 'show the fly the way out of the fly bottle.' Once this is done, we find ourselves back here, in our familiar world, no longer needing to do philosophy. The ideal solution is one which enables me to 'stop doing philosophy whenever I want to' because it is no longer needed. I am cured.

Somehow, to me, this doesn't seem enough. I believe that there is more work to do. Maybe that work is just more of the same, more 'dialectic of illusion' (as we scour the history of philosophy for suitable targets), but I wouldn't be so quick to make assumptions. We started off with the grand idea of 'defining reality'. I, for one, would be hugely disappointed if the *only* thing I could say is, 'Reality is these hands, this table, the tree I see through the window...'.

The idea that 'reality simply didn't begin with me' is where I was when I started the work which eventually became my book, 'Naive Metaphysics: a theory of subjective and objective worlds' (see My Oxford D.Phil thesis was all about the 'rejection of the ego and truth illusions' (see But was that it? everything? I was beginning to have my doubts. If the ego (or 'transcendental ego') is just an illusion, what's the reality behind the illusion? How do you explain, in a non-circular way, how the illusion arose in the first place? It's easy enough for me to do this in your case, explain *your* illusion, it's the existence of *my* illusion which seems so problematic.

I know what the younger me would have said: this is nothing but shameful backsliding. But I know of no other way to do philosophy than to consider all the elements of the problem or question, and not rest until one has a theory which is fully consistent, one which we can believe in without any sense of strain.

So I embarked on an investigation which little did I realize would leave me in a place beset by paradoxes. The theory can only be true (the theory of subjective and objective worlds) if we are prepared to accept the 'truth of a contradiction'!

The point of bringing up all this biographical material is that I composed the Metaphysics program with the intention of avoiding the 'two world' idea, if I could, or at least postponing it as long as possible. To a large extent, I think I succeeded. (Maybe I shouldn't say that, but leave you to judge for yourself.)

At any rate, we are still stuck with the question 'what is it that you now believe?' If reality is not constructed from 'this', then what is it made of? Can we ask that question, or, if not, what question can we ask? The solution I suggest in the program concerns the way we understand the notion of truth. Reality isn't 'made' of anything. It is just, as Wittgenstein stated in his Tractatus, 'All that is the case.' Making judgements about what is true or false is something *we* do, but it is part of the very notion of truth that we recognize a gap between verification and truth. Even if everyone agrees that witches exist, it is still possible that we are all wrong, that there are no witches.

The finesse here is that the idea that 'we could all be wrong' doesn't require some external observer or external perspective, in the same sense that the idea that 'I could be wrong' implies the possibility of 'another person'. It is not as if what I can't do for myself you can do for me (because the same question arises for you, leading to an infinite regress of 'third persons'). It is sufficient that I have the concept of truth, as something which is essentially public, not private 'property', something shared because it is the same for you and me, and indeed for all.

Is *that* what you now believe?

But isn't this idea of 'one truth for all' just a little bit worrying? What is truth, anyway? And so the dialectic continues.

All the best,


Friday, September 27, 2013

Could a computer that thinks also will?

To: Charles R.
From: Geoffrey Klempner
Subject: Could a computer that thinks also will?
Date: 29th November 2010 12:09

Dear Charles,

Thank you for your email of 19 November, with your third essay for the Philosophy of Mind program, in response to the question, ''A computer can think and make decisions, but it cannot WILL.' Is that a convincing argument against a materialist view of the nature of the self?'

This is a well argued, and indeed brave essay, in which you make major concessions to the arguments of materialism, in order ultimately to stake out a place for 'the sacred' as the object of an attitude of mind which turns away from the 'biological-material dimensions of existence and toward God, toward an interior, subjective, non-empirical experience of the Sacred.'

If I am reading this correctly, an artificial person, constructed by man, would be able to experience the Sacred in exactly the same way as a person who is 'natural born'. If we are, as you say, involved in chasing away, or pushing back, a 'God of the gaps' then we must surely not erect barriers which would prevent artificial persons from joining in worship alongside the rest of humanity.

But let's first retrace our steps. A being that thinks, you say, must also be capable of willing because thinking and willing are not two separate processes, they are part of a single capacity. One of your arguments is that every decision or act of willing is preceded by a thinking process whether we are aware of this or not. For example, as a competent driver I slow down on the motorway when I see traffic queues ahead. I don't have to consciously think, 'Uh huh, traffic queues ahead, must slow down.'

However, you could have just as easily argued that an act of will precedes every thinking process, whether we are aware of this act of will or not. Sitting in my attic at home, I decide to direct my thoughts (yet again) to that intractable philosophical problem which I will never solve, and yet which I will never give up trying to get to grips with. An effort is needed to maintain my concentration as I scramble about on the smooth rock face. Yet it is also true that any thought that I might think is an action, a 'mental act'.

We need to be a bit more precise about this, in order to deal with possible counterexamples. 'Thinking' is an action verb. To think is more than merely have ideas occur in one's mind. If you say to me, 'Don't think about dragons,' obviously I can't help having the idea of a dragon occur in my mind, but I can make the decision to think about something else. I can will the direction of my thoughts. Some thoughts may indeed seem involuntary, but then some physical actions are too.

Why can't present day computers will? The obvious answer is, 'because they can't think.' Every computer built up to the present day is basically a calculating machine. These machines have impressive capacities to represent states of affairs in the world and draw conclusions about them (e.g. Deep Blue, the chess playing computer that beat Gary Kasparov) but these representations are not *beliefs* because (I would argue) they are not *for* the entity that has the representations. This crucial notion of 'being for' is what makes the difference still (at the present time) between human beings and computers.

Before I take this any further, there is another issue to consider. The quote from Marvin Minsky arguably contains (by implication, though not explicitly) a non-sequitur. If the nervous system obeys the laws of physics and chemistry then, in principle, there could be an artificially produced physical entity which did everything that we can do so far as thinking is concerned. However, it does not follow that such a physical entity would be a Turing machine. The question of what else it could be is a matter of ongoing controversy, but the upshot is that it has yet to be proved that a biological organism works in fundamentally the same way (if you dig down far enough) as a computer. (A Turing machine is an idealized construction which every programmable computer has in common.)

So we have two thoughts: the first is that beliefs must be 'for' the entity in question. The second thought is that it may well turn out to be the case that what biology is able to create cannot be reproduced by means of an assembly of silicon chips, or in any similar manner.

In order for beliefs to be 'for' an entity, it must also have desires. An entity which has beliefs and desires would have to be an agent, capable of initiating actions in the world, in order to satisfy those desires. It follows that a computer which could 'will' would also be self-moving, as we are. If biology is necessary for thought, then this self-moving entity would have to be a biological organism. Perhaps this is what we are heading for: the first 100 per cent artificially constructed 'human being'.

And what, then, would be the consequences for religion? If we 'proved', finally, that we could do what previously it was believed only God could do would that make us Gods? Or would it be the final proof that there is no room for God in a material universe? I agree with you that the answer is, No. There is room for religion, room for the sacred. But the question is what this *means*. What is prayer, what does it mean, if it does not involve some form of communication or dialogue with the Eternal Thou? (to use Martin Buber's phrase). Is this actual communication, in some sense, or merely 'as if'? Are we, as in traditional religious belief, putting ourselves in relation to something actually existing outside us, outside 'material existence'? or, if not, what is the alternative?

All the best,


Berkeley's immaterialism and the attack on abstract ideas

To: Craig S.
From: Geoffrey Klempner
Subject: Berkeley's immaterialism and the attack on abstract ideas
Date: 26th November 2010 12:42

Dear Craig,

Thank you for your email of 17 November, with your essay on Berkeley written to your own title, 'Keeping up Appearances', and your essay of 22 November in response to exam question for the University of London BA Modern Philosophy: Locke, Berkeley, Hume module, 'Why was Berkeley so concerned to attack the theory of abstract ideas? How successful is his attack?'

Regarding your point about evolution of sensory organs, the hypothesis that there might have existed beings whose only mode of perception was through contact must be (given what we know) a hypothesis concerning a possible world where evolution favoured such beings. Mutations have to give sufficient advantage in the process of natural selection or the evolution of, say, an eye from a clump of light sensitive cells doesn't get started at all, even if such creatures would welcome eyes if we could give these to them.

Keeping up appearances

I can see where this is coming from, but it kind-of misses the point of Berkeley's dialectical attack on the idea of matter. In your story of a deity who devises a more elegant, less labour-intensive way of 'keeping up appearances', there are two ideas: the utility of space and the physical -- whatever the physical may turn out to be -- and the most elegant choice of laws of physical nature ('nothing carefully arranged' being high on the list of candidates).

Let's consider first the question of the distance that separates Descartes and Berkeley. Descartes rejected the idea of 'matter' as something that, once created, has its own 'existential inertia' that keeps it going. Just as with mental substance, material substance requires God's continual creative power to remain in existence from moment to moment.

It's a good question to ask about physics. Why do things continue? It's the sort of question to which one expects an interesting answer, not merely, 'Well they're things, aren't they? that's what things do.' But of course for Descartes, God is the one in charge of the laws of nature.

We believe in space and in the existence of material objects that occupy space. God is not a deceiver, so he would not allow us to believe this if it weren't true. OK, but how can God *make* it true? That was the question Berkeley asked himself. There's nothing God can do to make 'matter' because the idea is just nonsensical. There's no concept you can form of it that isn't based on our experiences of seeing, touching etc.

The most interesting difference between Descartes and Berkeley is that Descartes, in effect, starts with God. After the cogito, it is his proof of God's existence (from my 'idea of perfection' which must have a cause) which enables him to reclaim the universe of physics. Whereas with Berkeley, we start with a dialectical attack on the idea of matter and conclude that the only way to avoid a universe full of holes is to have God up there, managing our virtual reality.

Idealism as a philosophy, or rather a metaphysic, arguably began with Berkeley but then continued through a long tradition including Kant, Fichte, Hegel. Refuting idealism is no easy task (I make the attempt in the Pathways Metaphysics program -- you're welcome to have the course units if you have the time to look at them!). Kant's critique of Berkeley and Leibniz -- that they are playing fast and loose with the concept of 'experience' -- far from getting us out of idealism, just take us further in (the Berkeleian 'archetypes' in God's mind become unknowable 'noumena' or 'things in themselves').

To cut to the chase: the error, if there is one, is the idea that what we are given, ultimately, is experience and the task of the philosopher or metaphysician is to make the best sense of it. I think this is wrong, for broadly the reasons given by Rorty in his 'Philosophy and the Mirror of Nature'. This debate isn't new (it is played out, e.g. in the correspondence between F.H. Bradley and William James). To refute Berkeley you have to prove that the self is, first and foremost, a physical agent (see, e.g. John Macmurray's Gifford Lectures published as 'The Self as Agent' and 'Persons in Relation', unjustly neglected by contemporary academic philosophers).

Berkeley on abstract ideas

This is an excellent essay, sharply focused on the question, with which I could find little to disagree.

I think you are right to imply that Berkeley's attack on (what he takes to be) Locke's doctrine of abstract ideas merely 'supports' his attack on the idea of matter. It's not as if Berkeley's immaterialist view crumbles when you point out that he is wrong about Locke, or that, as you say, similar difficulties apply to his notion of a 'finite spirit'.

Having said that, it still seems to be to be a valid point that the naive or pre-philosophical notion of 'matter' (as that whose existence and continuity in 'space' requires no further explanation because that's just what things do) involves a mental operation which one might term 'illicit abstraction'. We convince ourselves that we have a concept which we don't in fact have. But that's just the diagnosis of the error made by his opponent, not the actual proof of Berkeley's theory. Generations of students who learn how to 'refute' Berkeley mistake the diagnosis for the proof.

If we allow the necessary adjustments, is the Locke/ Berkeley theory of concepts acceptable? Arguably, no, because it still depends on a problematic notion of 'abstraction' as the main process by means of which concepts are formed. You are shown lots of red objects and you form the concept 'red'. You are shown lots of square objects and you form the concept 'square'. Peter Geach in his book 'Mental Acts' mounts a powerful attack on abstractionism from a broadly Wittgensteinian perspective. We don't form concepts in the manner of pattern-recognition machines; we learn to follow rules, which is necessarily a practical ability. You have to have the concepts of colour or shape before you can even form the idea that there is something that these objects have in common in respect of their colour or in respect of their shape. A whole raft of concepts have to be acquired together. Locke is wrong to suppose that one can start with the simplest ideas and build up.

Does this point make any real difference to the Locke-Berkeley debate (if there is one) or indeed to Berkeley's immaterialist theory? In my comments on the first essay, I said that the crucial move was from the primacy of experience to the primacy of action. This is also the idea which underlies Wittgenstein's considerations on rule following and 'forms of life'. The interesting question, it seems to me, is whether one could take on board Geach's criticisms of abstractionism while remaining within a metaphysic of experience, i.e. idealism in the broadest sense.

All the best,


Leibniz on necessary and contingent truths

To: Scott B.
From: Geoffrey Klempner
Subject: Leibniz on necessary and contingent truths
Date: 23rd November 2010 12:16

Dear Scott,

Thank you for your email of 15 November, with your essay for the University of London BA module Modern Philosophy: Spinoza, Leibniz, Kant module in response to the question, 'Does Leibniz's account of truth allow for contingent as well as necessary propositions?'

I fully sympathize with your difficulties regarding the understanding and interpretation of Leibniz's philosophy.

It is relatively easy to answer the question: Yes, if you are prepared to make the required concessions, Leibniz's theory of truth does allow for contingent as well as necessary propositions. A proposition is necessary if it is true in all possible worlds. A proposition is contingently true if it is true in the actual world but not in other possible worlds. An actual world is fully determined by the individuals which comprise it. Any alteration in an individual would give rise to a different possible world. So it follows that a statement which is contingently true about, say, SB, consists in the attribution of a predicate to the subject, SB, whose individual concept 'contains' that predicate.

This is a weird notion of 'contingent truth'. Our pre-philosophical understanding of the nature of a statement about an individual is that any given predicate contingently might, or might not apply to that given individual. Philosophers distinguish between 'essential' properties like being human from 'accidental' properties like being a philosophy student, although intuitions about this are vague. For all I know, SB might be an intelligent android created by aliens in order to investigate Earth people. In this case, it would be quite plausible to say that if this turned out to be the case, I didn't 'really know' SB. It would be very odd to say that I know who SB *is*, but it is still logically possible that SB is an android and not a human. However, we find it utterly bizarre to claim that someone who doesn't know what marks SB will gain for his Modern Philosophy: Spinoza etc. module doesn't know 'who SB is'.

So, even if we accept that Leibniz's account of truth 'allows' for a distinction between contingent and necessary propositions, in his terms, it remains the case that Leibniz's notion of what a 'contingent proposition' is, is one that we find difficult to believe, to say the least.

The real question, is *why* did he hold this view?

This is where Leibniz leads students of his philosophy on a merry dance. Your essay contains a number of claims to the effect that Leibniz held A because he held B, and held B because he held C; but what really comes first in an explanation of the process of reasoning which leads to the claim about necessary and contingent propositions?

Russell thought he knew. In his book on the philosophy of Leibniz, Russell argued that the key to Leibniz's philosophy, and in particular to his view about the nature of individuals lay in his inability to see any alternative analysis to the Subject-Predicate form. At the time when Russell was writing, the idea that there could be relational truths was something radical. Previous philosophers had failed to grasp the point that Russell saw, that relational truths can be primitive, not analysable into non-relational propositions. Leibniz merely saw with greater clarity the consequences of failure to admit relational truths. Leibniz is an object lesson in what happens if you fail to give a correct analysis of relational propositions.

I don't believe that diagnosis, and I don't think there are many commentators on Leibniz who would agree with Russell today. So the hunt is on to find a better explanation.

I think that the explanation starts with Leibniz's account of the nature of space, and his response to Cartesianism. Like Berkeley, Leibniz was sceptical about the idea of an all-powerful being who might, or might not create a world of matter in space corresponding to our experience depending on whether or not he was sufficiently benevolent not to allow us to be 'deceived'. From Berkeley's point of view, there is no 'deception'. When we look out onto the world we are looking at the inside of God's mind. The things we call 'material objects' are merely 'ideas'. Leibniz proposes a different, more robust account of the nature of existence. Every object has its 'point of view' on the world. Add up all the points of view and there *is* nothing else, no empty 'space' for objects to exist 'in', as Newton (and Descartes) believed.

We can state this in terms of what God chose to create, but God doesn't really play such an important role (at least, not as important a role as He plays for Berkeley). In order to create the object SB, God had to create the universe as seen from SB's point of view. SB doesn't have this knowledge (as you state), the reason being that his perceptions are more or less 'confused'. However, when you describe all the points of view -- of entities which we term 'non-sentient' as well as those we term sentient or intelligent -- you have described the universe.

Leibniz's metaphysics was taken up by the academic philosopher Wolff, and it was Wolff's metaphysical system that Kant lectured on. From Kant's viewpoint, Leibniz's theory of monads was an attempt to state, in terms of 'experience' truths the nature of which go beyond the bounds of possible experience. His 'monads' are Kant's 'things in themselves' or 'noumena', the ultimate constituents of the universe of which we can form no positive conception for the very reason that they transcend the bounds of possible experience.

All the best,


Philosophical significance of the paradox of the heap

To: Damiano S.
From: Geoffrey Klempner
Subject: Philosophical significance of the paradox of the heap
Date: 19th November 2010 11:14

Dear Damiano,

Thank you for your email of 10 November, with your first essay for the Philosophy of Language program, in response to the question, 'How would you explain to a non-philosopher the philosophical significance of the paradox of the Heap?'

I found the English to be excellent. I had no problem at all in following your meaning.

It's interesting that you start off with the question, 'Is it possible to construct a logically perfect language?' I think you'd agree that for the non-philosopher this is a rather strange and arcane question. 'Perfect' in what way, exactly? And what is 'logic'? However, a way to motivate this idea would be to point out something that we all recognize, that, somehow, without agreeing on precise definitions of the words we use, we are nevertheless able to convey useful information to one another by means of ordinary language. Yet sometimes we fail, and misunderstandings arise. Who has not experienced the frustration of finding yourself arguing with a friend over a trivial matter, an argument which could so easily have been avoided had one of you expressed themself a bit more clearly.

This motivates the attempt to find better, clearer words to express what we mean. But a logically perfect language? When would we need this, and for what purpose?

I have spent a lot of time thinking about how persons with no previous experience of philosophical thinking can be helped to grasp what philosophers are trying to do, the point of it all. As philosophers, we need to think about this, just to keep ourselves honest. With regard to this particular problem -- the paradox of the Heap -- it is incredibly difficult to motivate learners to think of the paradox as a serious challenge, as something more than merely verbal trickery. They just don't get it. You try explaining it, on someone you know who has never done philosophy before!

As good philosophy students, we learn the importance of logic. We acquire the greatest respect for a logical argument, set out in clear, persuasive steps. The paradox of the Heap is gripping because the steps are so clear, so undeniable -- while the conclusion is so clearly false. How could we get into this mess? Yet, to the non-philosopher, the whole thing is just ridiculous. I think that's a paradox too. The paradox of 'the paradox of the Heap'.

If one was looking for a premise to question, it would be the principle of mathematical induction. As good logicians, we 'see' immediately that what applies to 1 and applies to n+1 if it applies to n, must therefore apply to all the members of a numbered series. You just keep 'doing it', performing the very same action, over and over again for 1, 1+1, 1+1+1, 1+1+1+1 etc. But isn't this begging the question? We know we *can't* just repeat the process endlessly. We know, from experience, that as the numbers rise, so our confidence in applying the predicate in question (e.g. 'non-heap', or 'bald') to the next member in the series falls until we reach a point where the question is just indeterminate. Is it a heap or not a heap? Is the man bald or not bald? We just don't know what to say in this particular case.

Looking at this more closely, and comparing it with mathematical induction as used in arithmetic to prove theorems, it seems to me that there is an important distinction between the mathematical and the empirical case. In the case where we are hypothetically adding grains of sand, one by one, it is *not* true that we are doing the 'same thing' over and over again. Adding one grain to a few scattered grains on the floor is not the same thing as adding one grain to a large number of grains which are beginning to heap up. It's not the same action. That's what someone who had not been 'brainwashed' by a logic course would say.

Moving on to the idea that there is an ideal physical description of the world, at the fundamental level, this does seem easier to motivate. Science is all about precision. In everyday life we express ourselves as precisely as the situation demands (although, as I indicated, sometimes we make a bad judgement call and fail to be sufficiently precise). But science, as you say, aims to give an 'objective' description, it aims to say 'how things are' in themselves and not merely pick out salient features depending on our interests. The problem here is that, in attempting to omit the subjectivity of human perception and interests, we find that we have failed to describe reality completely. We have left a whole lot of stuff out.

What is so interesting about this -- especially for non-philosophers -- is that this isn't anything to do with a 'soul' or Hamlet's 'more things in heaven and earth than are dreamt of in your philosophy'. You can't reduce psychology to physics. Whereas physics might attempt to describe its subject matter with complete precision, psychology can't do this. Donald Davidson accepts this point. He calls this the 'anomalousness of the mental': see his article 'Mental Events'. (David Chalmers goes further, I think, in denying the claim about supervenience: his 'zombie' argument hypothesizes two entities which are physically identical, but one is a zombie while the other has consciousness. The point of his argument is we *don't know* or *can't prove*, on the basis of all we know, e.g. about neurophysiology, that this situation could not arise.)

All the best,


Monday, September 16, 2013

Zeno's paradoxes and the nature of motion

To: Alistair L.
From: Geoffrey Klempner
Subject: Zeno's paradoxes and the nature of motion
Date: 12th November 2010 13:11

Dear Alistair,

Thank you for your email of 4 November, with your essay for the University of London BA Greek Philosophy: Plato and the Presocratics module, in response to the question, 'What do Zeno's paradoxes demonstrate about the nature of motion?'

I think it was a good decision to look at all of Zeno's paradoxes and not just those which specifically address the concept of motion. I agree with you that they are all, in different ways, relevant to the question.

The basis of your argument is an important distinction between the 'reality' of motion, in the physical world, and our 'models' of it. We deal with things in motion including our own bodies at the most basic level without having to reflect on it. It is when we bring our 'higher mental faculties' into play, in an attempt to coherently model our own movements or the motions that we perceive, that the trouble starts.

Following on from this distinction, there are two sorts of consequences that one might seek to draw from Zeno's paradoxes regarding motion: consequences for the nature of motion itself, which would in effect be a priori knowledge of the physical world; and consequences for the nature of our models of motion, which might lead to a Kantian-style claim to the effect that our knowledge of external reality is constrained by conditions which apply to any possible model of physical motion. (In stating this distinction, I am merely drawing out the implications of what you say in your essay. I am not claiming that the distinction is necessarily valid, or even that I fully understand it.)

Parmenides had set the example for philosophical arguments which have direct, a priori necessary consequences for the nature of reality. Zeno, who as you report say himself as following in Parmenides' footsteps would have attempted nothing less. Whereas we (post Kant) are much more inclined to talk of limits on the way we model reality, on what is or could be an acceptable physical theory.

Your 'short answer' to the question is, No, Zeno's paradoxes don't demonstrate anything about the nature of motion. 'What Zeno does is demonstrate quite important questions about the nature of our models of motion and in doing so questions our models of space, time and reality in general... there is still the ever-present gap between our models and reality itself and while the investigation of Zeno's paradoxes has led to better justification of these models there is no guarantee that they are what reality is.'

I am not sure that I fully understand this claim. Let's go back to the distinction I described earlier. Physical motion, as a thing in itself, is something out there which we discover through action and sense perception. Although we may be confident that it exists, we only 'know what it is' to the extent that we are able to describe models, formulate theories, in short, do the maths. According to the maths, the sum of an infinite series can be finite. Again, according to the maths, the rational numbers cannot be put in 1-1 mapping with the real numbers (*if*, as you say, you accept Cantor's proof). Both of these results are arguably needed in order to deal with Zeno's paradoxes, and that is an important discovery -- something the Greeks didn't know.

How do our models still fall short? You say at one point, 'The concept of the limit of a convergent infinite series is a useful mathematical tool and provides a definition that solves problems like those in these two paradoxes but the limit is not actually in the series so if you do take Achilles as traversing an infinite number of smaller and smaller distances on his way to catch the tortoise the last step from the end of the infinite series to the limit (position of the tortoise) is not part of the model.'

But according to the model there is no 'last step', no 'end of the infinite series', so long as we follow Zeno and have Achilles approach the tortoise step-by-step. The solution, surely, is to distinguish between actions that Achilles does, and the series of distances that he traverses. He traverses an infinite series of distances but this does not require an infinite series of actions.

I agree that one can't just say, 'If you accept the maths, then there's nothing more to say about the reality.' Space (and time) *might* be quantized. So what if they were? All the problems Zeno raises would disappear. The arrow *is* at rest, in effect, because what we term 'motion' is merely the result of a cinematic illusion (Bergson opposed his 'duree' to what he termed the erroneous 'cinematic model' of movement and perception). The arrow is at rest here, then here, then here. The only residual difficulty would be with the moving rows, but that's easy enough to deal with if you distinguish absolute motion (an object occupying successive 'slots' as in a Lego brick) from merely relative motion.

All the best,


Locke on primary and secondary qualities

To: Craig S.
From: Geoffrey Klempner
Subject: Locke on primary and secondary qualities
Date: 12th November 2010 11:56

Dear Craig,

Thank you for your email of 4 November, with your essay for the University of London BA Modern Philosophy: Descartes, Locke, Berkeley and Hume module, in response to the question, 'What role does the notion of resemblance play in Locke's account of the distinction between primary and secondary qualities? Is his account of the distinction a defensible one?'

Thanks also for your comments on my piece, In Pursuit of the Amoralist. My argument is 'Kantian' in the sense that I am looking for an a priori basis for moral judgement, but it also sharply diverges from Kant's view that we can derive a moral theory, the laws of ethics, by deduction from the Categorical Imperative. My approach is necessarily more modest.

The point you might have missed concerns the role of the statement, 'Other persons are not my measuring instruments'. I claim that this follows immediately from the idea that there is such a thing as truth. For the solipsist, there is ultimately no distinction between how I judge things to be, and how they are in reality. This is not as such a moral claim. Rather, the existence of other persons is a 'necessary condition for the possibility' of there being a notion of truth (to put the claim in Kantian terms). However, it follows that I cannot make a meaningful distinction between needs or interests depending on whether they are 'mine' or not. That is the minimum basis for an idea of moral conduct, but of course it still leaves much undecided.

Back to your essay.

Your sanguine defence of Locke had me searching my hard drive for an exchange I had with another of my UoL students on the same topic, back in March/ April 2006! We were looking for a quote which I seemed to remember from Locke's Essay to the effect that angels would be able to 'see' the corpuscles that constitute the gross bodies that we perceive. I think we did subsequently find the passage, although I don't have the reference to hand.

Let's say that angels have 'eyes'. How do they work? Evidently not by processing perceptual information acquired through a process analogous to the way our eyes work. (In theory, of course, they could but then we would be on the road to an infinite regress, with angels speculating about super-angels etc.) Let's assume the regress doesn't even get started: angels don't perceive through action at a distance on their sense organs. They interact directly with the corpuscles, feeling them, holding them, moving them in Helen Keller fashion, relying on proprioceptive feedback. That might work.

In theory, there is no reason why we need to have organs of sight, hearing, smell etc. Helen Keller-like beings could develop artificial tools for accomplishing what we are able to do by the gift of nature. A long time ago, I saw a piece on Tomorrow's World where a blind man was able to 'see' by means of a video camera which etched an image into his bare back by means of hundreds of needles. Ouch!

You claim that Locke's account is confirmed by science, but also, interestingly, argue that it would survive the discovery that 'mass, shape, size etc. turn out not to be the best way to understand matter. Locke's primary qualities would be unseated. Fair enough. We could abandon the term as outmoded or restrict it to properties deemed fundamental by current science.' Really? What reason do we have for holding that human beings, as a matter of logical necessity, have the capacity to acquire information about the world in a form which *represents* or *resembles* how things are, not just in the sense of structural isomorphism derived from theory, but in terms of content -- as our idea of, say, a spatial array is considered (still) applicable to particle physics?

The very next point you make is crucial here: 'Indeed 'solidity' was already dubious when Locke introduced it.' I say. It was in fact Leibniz who diagnosed the fundamental weakness in Descartes' account of material body. You can't derive physics from geometry alone. The extra something -- impenetrability, solidity, resistance to movement, mass -- all these notions are incapable of being derived from the idea of 'extension', where as in Descartes the visual sense is taken as the primary model perception.

On this account, if any property deserves to be called 'primary' it is the capacity to exert a force through physical contact. As a matter of logical necessity, any subject of experience must be capable of acting upon the world of their perception. Everything else, including the capacity for sense perception at a distance, is up for grabs.

Locke may have thought that it was sufficient to report on the 'best science' of his day. This science was itself the product of philosophy. Greek atomism played an important part, although Newtonian corpuscles are a very different animal from Democritean atoms. But the way he describes his distinction between primary and secondary qualities makes it look as though he has discovered a necessary truth about the very nature of perception, as it applies to any conscious subject in any conceivable physical world. That claim is wildly overstated.

All the best,


Examining our naive ideas about the soul

To: Anna H.
From: Geoffrey Klempner
Subject: Examining our naive ideas about the soul
Date: 11th November 2010 13:08

Dear Anna,

Thank you for your email of 2 November, with your first essay for the Philosophy of Mind program, in response to the question, 'Explain the different facets of our ordinary, pre-philosophical idea of the soul, giving examples that relate to your own experience. What impact does philosophical enquiry have on those ideas?'

There is a lot of meat in this essay. You start with an account of what you learned about the 'soul' through your Catholic upbringing, then go on to discuss the different accounts of the soul in Plato and Descartes, as well as raising difficult questions about the relation between the concept of 'soul' and the concept of 'mind'.

Did Plato ever talk about damnation, as such? The belief that souls come to reside in Hades was common in Plato's time. But in Phaedo I don't recall that the term 'Hades' is ever used. Socrates (as the mouthpiece of Plato) talks about the eternal Forms, and how he soul is 'akin' to the Forms, and must therefore take delight in the prospect of being released from the material body at death. The aim of philosophy is to prepare our souls for the afterlife, by contemplating the Forms.

So there is at least the implication that, the more the soul is 'prepared', the better it will enjoy the afterlife, although Plato never talks of what happens to the souls of those who neglect their studies for the pleasures of the flesh.

Plato was aware of the Pythagorean theory of reincarnation. In the Meno, he says that the soul existed before it became embodied, and this is the explanation of how we come to possess a priori knowledge. We 'knew' the Forms before we came to know material things. So the soul comes to inhabit a body, and then leaves it. Having left, it remains permanently in the company of the Forms.

When Plato considers the question of why we should be just, or moral, in the dialogue Republic, the argument is all about how the immoral man 'suffers' as a consequence of his actions in *this* world, because of his 'disordered' soul. In other words, our true self-interest lies in behaving justly, because only in this way can we be truly 'happy'.

Although Christianity took much from Greek philosophy, the idea of a Day of Judgement when each soul will be consigned to Heaven or Hell is not one you will find in Plato or Aristotle. Implicitly, the very idea contradicts Plato's view that wrongdoers cannot be truly 'happy'. There is no need for a supra-human institution of cosmic justice where the good are rewarded and the bad are punished in the afterlife.

How exactly does Descartes' view of the soul differ from that of Plato?

For Plato, as more explicitly in Aristotle, the soul is the 'Form' of the body. However, Aristotle, unlike Plato, saw the Forms as not residing in a separate universe but rather part of this world. The Form of the living human body is something like its functional, organizing principle which accounts for the kinds of thing that human beings can do which set them apart from other things in general and other living things in particular: such as the capacity for reasoning.

By associating 'form' with 'characteristic function', Aristotle makes no distinction between the mind and the soul: they are one and the same. The Greek term 'psuche' can be translated as 'soul' or 'mind'.

Descartes, from a contemporary perspective, represents a reaction to the Aristotelian view, in his insistence on viewing the self as a substance, distinct from physical substance. It is 'mental substance'. All the properties that we associate with the mental are properties of the soul. So here too there is no distinction between 'mind' and 'soul'.

However, it is interesting that in contemporary philosophy there is still debate over the question of dualism, even when it is accepted that Descartes' view of the function of the brain was incorrect. The brain is not, as Descartes believed, a mere 'relay mechanism' (the soul interacts with the 'animal spirits' in the pineal gland), but rather the very source of our thinking processes. How could you not be a materialist if you believe this?

And yet there are contemporary dualists who accept the role of the brain, but argue that something else is produced by brain activity, besides bodily movements and speech, something of which only the subject can be aware. On this view (as you will see in the program) there arises the strange possibility that there might be a zombie indistinguishable from a human being in every external respect. The only difference would be internal: there is nothing 'it is like' to be a zombie because 'all is darkness within'.

You and I know that this is not true of us. But if you tried to convince me, or if I tried to convince you, we could never succeed, for the very reason that a zombie (by hypothesis) would do and say exactly the same things!

Could this extra 'something', that makes the difference between a human being and a zombie, be the 'soul'? In the program, I offer various considerations against this view. What seems clear, however, is that talk of the mind and what it does in a purely 'functional' way leaves the question of what, if anything is 'inside' unanswered.

All the best,


Leibniz's Law and opaque contexts

To: Radhika R.
From: Geoffrey Klempner
Subject: Leibniz's Law and opaque contexts
Date: 11th November 2010 12:17

Dear Radhika,

Thank you for your email of 2 November, with your essay for the University of London BA Logic module, in response to the question, ''Someone might believe that George Eliot wrote Middlemarch without believing that Mary Anne Evans did, even though George Eliot is Mary Anne Evans.' Discuss.'

In your essay you have answered the question by offering an exposition of Frege's theory of sense and reference in his essay 'On Sense and Reference' ('Uber Sinn und Bedeutung'). This is good so far as it goes. A reader would gain some understanding of the problem raised for the principle of substitutivity by the phenomenon of propositional attitudes, and also of Frege's view of the problem and his solution to it.

You get credit also for referring to Leibniz's principle of the indiscernability of identicals and also to the principle of substitutivity (identity substitution). You could also have said something about how the two principles are connected, in particular, how it is that the second principle sometimes fails even though the first principle is taken to definitive of what we mean by 'identity'.

Even if the question were focused more narrowly on Frege's explanation, however, an examiner would expect you to do more: e.g. to offer criticisms of Frege's theory and possible responses to those criticisms. Do you agree with Frege? Can you see any potential difficulties with his account?

For example, is it true that every proper name is associated with a particular sense, as Frege seems to imply? Consider the examples of '10+2' and '4x3'. These expressions are good examples for Frege's theory, because they display the 'route to reference' on their face. Computing the function 'plus' for 10, 2 gives the same result as computing the function 'times' for 4, 3. The route to reference is different even though the reference of each expression, 12, is the same.

In natural language, definite descriptions work in a similar way: The director of Pathways to Philosophy is GK. The owner of the white Reliant Scimitar GTE parked on Chesterfield Road is GK. Computing the 'function' in each case takes you to the same object, GK.

But proper names are not like this. It seems implausible to suppose that a proper name is equivalent to some particular description, nor does it seem plausible to hold that every speaker has the same understanding of a given proper name, such as 'Mary Anne Evans'. How do you distinguish the Fregean 'sense' of a name from various beliefs about its bearer? Where do you draw the line? Even if we go along with Frege and accept that in addition to the actual referent there is an explicit route to reference or mode of presentation of the object referred to in the case of the mathematical expressions or in the case of definite descriptions, it is harder to accept that a similar explanation applies to common or garden proper names.

But does it really matter if each speaker associates a different Fregean 'sense' with a given proper name? So long as there is agreement over the reference, there would be no misunderstanding. Perhaps we don't need to distinguish between the sense of a proper name and beliefs about the bearer or 'informational content'. What do you think?

I once heard a paper where the philosopher P.F. Strawson described proper names as analogous to a card index system. When you hear a 'new' name you write out a card in your mind, which might remain blank. Then, as you acquire more beliefs, you add entries to the cards. One card might be 'George Eliot' and another card might be 'Mary Anne Evans'. Then you discover the vital piece of information that the two names refer to one and the same person. So now you can add this further information to the two cards, in the form of a cross-reference: 'Mary Anne Evans (see George Eliot)'. This seems initially plausible. Can you think of any objections?

Probably the best defence of Frege can be found in Michael Dummett's brilliant, but lengthy books: 'Frege: Philosophy of Language' and 'The Interpretation of Frege's Philosophy'. Since Quine, contemporary philosophical logicians have generally been sceptical of Frege's notion of sense. Probably the most well known critique, together with the beginnings of an alternative approach to an account of the truth conditions for indirect discourse is Donald Davidson's paper 'On Saying That'.

As the question does not explicitly refer to Frege, you would be expected to at least show that you are aware of alternative accounts, as well as criticizing or evaluating Frege's theory.

This is work you have got to do for yourself. Any good text on Philosophical Logic will offer guidance on this, as well as books and articles that you could refer to. A good starting point is the chapter on Logic in A.C. Grayling Philosophy: A Guide to the Subject.

As it stands, your essay earns credit for clarity but would lose marks for failing to do much more than offer an exposition of Frege.

All the best,


Friday, September 13, 2013

Fairy tales and the coherence theory of knowledge

To: Emelie G.
From: Geoffrey Klempner
Subject: Fairy tales and the coherence theory of knowledge
Date: 10th November 2010 12:27

Dear Emelie,

Thank you for your email of 1 November, with your essay for the University of London BA Epistemology module, in response to the question, ''The fact that there are coherent fairy tales shows that one might have a coherent system of beliefs without those beliefs amounting to knowledge.' Discuss.'

This is a good essay which is well up to the standard of work produced by my other University of London students.

A great deal of work has been done on this topic by contemporary epistemologists, and an examiner would not expect you to be able to summarize all the various positions right up to the current state of debate. For example, you don't discuss the contrast between 'internalist' and 'externalist' accounts of justification in terms of coherence. That would possibly be a relevant consideration, but, as I said, you are not expected to summarize the entire debate given the limited time available for answering the question.

What are you expected to do? Answer the question. That entails saying enough to show the examiner that you are fully aware of exactly what the question is.

Here, arguably, you have been a little imprecise, in seeming to conflate a coherentist theory of knowledge with the coherence theory of truth. Suppose the question had been, ''The fact that there are coherent fairy tales shows that one might have a coherent system of beliefs, many or most of which are in fact false.' Discuss.' That is an objection targeted against a coherence theory of truth. You cite Brand Blanshard who is perhaps one of the best known defenders of a coherence theory of truth. However, one might question whether a response to the objection against a coherence theory of truth, along the lines adumbrated by Blanshard, is needed in the case of a coherence theory of knowledge. It is perfectly possible to hold a coherence theory of knowledge while at the same time rejecting a coherence theory of truth.

Another point at which we need to make an important distinction concerns the aim of a 'theory of knowledge', in the sense of a definition of 'S knows that p' in terms of necessary and sufficient conditions. There is no necessary entailment between a definition of knowledge in this sense and an adequate response to the full-blooded sceptic. Suppose we had an adequate answer to the objection to coherentism about knowledge posed in this question. One is not thereby armed against any or all objections that might be raised by a full-blooded sceptic. The response to scepticism might require a different strategy, perhaps a strategy on which holders of competing definitions of knowledge in terms of necessary and sufficient conditions could agree.

Why be a coherentist about knowledge? You give the most compelling consideration: that coherentism is a reaction to the implausibility of foundationalism. There just aren't enough foundational beliefs around on which to base the edifice of knowledge. (You could have added that this is much more evident given that we have rejected traditional foundationalist theories which identify foundational propositions as those concerning, e.g. sense data.)

If that's true, however, how can we fail to be coherentists of one kind or another? We have to accept that tracing back the regress of explanation/ justification will eventually take us in larger or smaller circles. Why is that so bad?

I think here that, without conceding the case to the contemporary foundationalist, more can be said about the structure of knowledge. Not all beliefs are the same. In particular, special considerations apply to beliefs based directly on experience -- notwithstanding your example of Jane who 'insists that she sees flying green horses in the sky.' Do we just take her word for it? Are we stuck at the point of insisting that *we* don't see them, even if she does? But, surely, there is much more to say about *how* we perceive. Suppose we ask Jane to take a photograph of the green horses that she sees. Then we look at the photograph together. How many horses are there? Exactly what shade are they?

Suppose one accepts that, in principle, a sufficiently resourceful Jane could weave a wonderful story justifying every claim that she makes, despite all the seeming evidence to the contrary. (I once had an evening class student who believed that the earth was flat.) Isn't this really a worry about scepticism, rather than a worry about the concept of epistemological justification? Accept that the flat earther, or the green horse believer, cannot be persuaded by any argument, no matter how ingenious. I'm not going to have any sleepless nights worrying whether maybe the earth is flat or that there really are green horses that for some reason I can't see. Accepting the existence of flat earthers or Janes is consistent with holding that the best analysis of justification that we have necessarily involves appeal to coherence.

I have been talking (as in fact you have) as if foundationalism and coherentism are the only alternatives. Your brief mention of Gettier, however, suggests further possibilities such as a causal theory. Why can't we simply take all the best bits from all the theories and say that there are relatively foundational propositions (though not enough of those); that coherence and causation are also involved? In that case, the objection in the question can be accepted as a rejection of an overly simplistic account of coherence, but one which is easily met if we are prepared to complicate our theory a little.

All the best,


Hempel on the symmetry of explanation and prediction

To: Mark S.
From: Geoffrey Klempner
Subject: Hempel on the symmetry of explanation and prediction
Date: 10th November 2010 11:31

Dear Mark,

Thank you for your email of 30 October, with your essay for the University of London BA Methodology module, in response to the question, ''Whatever suffices for explanation suffices for prediction and vice versa.' Discuss.'

This is an excellent essay with which I can find very little to disagree. I think you've really hit the nail on the head with your explanation (!) of why counterexamples to Hempel's symmetry thesis arise in the first place; that although citing the cause of an event explains the occurrence of that event, there are cases where we are able to predict an event on the basis of an observation which does not reveal the cause of that event, e.g. because both observation and predicted event are results of a prior cause, and also cases where we successfully explain an event which we could not have reliably predicted. e.g. because our ability to identify the cause depends on the wisdom of hindsight.

Also, I don't find that I am in any disagreement with you regarding the irreducibility of our notion of a cause (given your previous essay and my comments, some of which you have incorporated into this essay). As a Humean (in the widest sense) about causation, I don't believe that I have any handle on the concept of causation other than the idea that things we call 'causes' and 'effects' are particular instances of the workings of laws of nature. This is consistent with holding that causation cannot, as Hempel's DN model claims, simply be reduced to deductions of instances from a covering law and initial conditions. In my previous email, I suggested that agency and our ability to intervene in the course of nature was a major component in the idea of causation. This is my explanation of the point you acknowledge in your essay, that the concept of a cause is embedded deeply in our conceptual scheme. As subjects of experience we are necessarily and not accidentally agents.

You talked very confidently about what is, or is not, an 'explanation'. I did wonder, however, whether at least part of the answer to this question involves something to do with the question why, as observers and also as agents, we are interested in explanations. If explanation is knowledge, what kind of knowledge is it? If it is a tool, what kind of tool? Are all explanations (as Lewises rather simple thesis seems to suggest) all basically of the same kind?

I'm thinking particularly of a thesis memorably stated by Hilary Putnam, originally in a series of lectures which I attended at London University, and subsequently published in his book, 'Meaning and the Moral Sciences', which is that explanation is 'interest relative'. Suppose you asked a criminal 'Why do you rob banks?' The criminal answers, 'because there's more money in banks than there is in gas stations.' Whereas, you were looking for an answer to the question why he is a criminal (e.g. 'Because I had a deprived childhood and fell in with a bad crowd').

This interest relativity becomes much more apparent in the 'moral sciences', in history, psychology, sociology etc. which surely are just as relevant areas of explanation and prediction as physics or chemistry. Arguably, even if we accept the interest-relativity of explanation, this leaves the link with causation intact. If your interest is reducing the number of persons who take up bank robbery as a profession, then the causes in question are those relating to social deprivation or the failure of prisons as a means of reform and rehabilitation, whereas if your interest is in reducing the number of bank robberies, then the causes in question relate to the lack of sufficient security which make banks attractive targets for criminals.

So far so good, but it seems to me that once we leave the paradigm of the core sciences and consider explanation in its wider context, it becomes progressively harder to maintain Lewises thesis. Why does Beethoven choose a cello to play a passage where you'd expect to hear a violin? Why does Pip in 'Great Expectations' risk his life to save Mrs Haversham? (Why, for that matter, am I having such difficulty thinking up good examples? Does 'I'm not feeling very creative today' involve some kind of implicit reference to causal history?)

Anyway, you get the general picture. 'Explain' is a concept which is put to a variety of uses, as indeed is 'cause'. But why should there be an interesting or simple account of how the two concepts are related?

What this shows is not that you are wrong in claiming an important link between causation and explanation, but rather that it is worth asking the question, Why does citing a cause or causes satisfy our desire for explanation in the way that it does? What more general phenomenon is this (identifying a causal pattern or relationship) a particular example of? An answer to that question would strengthen your case rather than weaken it.

All the best,


Kant's refutation of idealism

To: Geoff C.
From: Geoffrey Klempner
Subject: Kant's refutation of idealism
Date: 5th November 2010 12:48

Dear Geoff,

Thank you for your email of 30 October, with your second essay for the Metaphysics program, in response to the question, 'Give a careful account of Kant's second 'Refutation of Idealism'.'

Your answer demonstrates a very good grasp of the essential core of Kant's argument against the 'idealist'.

We may assume that 'idealism' -- or whatever is the intended target of Kant's argument -- entails the view that experience is nothing but a temporal series of representations, whose content logically need not be linked in any particular way. To say that the content 'need not' be linked is consistent with observing that it is in fact linked in our experience. The point, however, is that to the idealist (or this kind of 'idealist') this is a purely contingent matter.

What Kant aims to disprove is the assumption of contingency. Moreover, what he claims to be necessary is not only 'some' degree of linkage between the representations in the temporal series but a very particular kind of linkage: they must be such as one could meaningfully hypothesize to be the result of *perception* of *objects arranged in space*.

In short, as you explain very clearly, the concept of space is an a priori requirement for experience as such, for without this there is nothing to bind the series of momentary states into something recognizable (and recognizes itself as) a 'self'.

As you state, 'The Egocentric Subjectivist is refuted because if there is nothing outside of us there cannot be an us at all.'

If you look at Kant's argument in its original context in the second edition of the Critique of Pure Reason, however, there questions which this brief account leaves unanswered.

Right at the beginning of his exposition, Kant states that he is not concerned to refute the 'dogmatic' idealist who claims that the very concept of space is 'impossible' but only the 'problematic' idealist, i.e. Descartes, who raises the question how I can know that there exists an external world, on the assumption that I know that I exist.

Descartes seems a million miles away from the 'Egocentric Subjectivist'. He never considers the idea that all there is might just be 'this experience'. For him, the limits of scepticism reach to the point where we are undecided what is the *true cause* of this experience, whether it is, as our senses seem to tell us, the perception of external objects in space, or, alternatively, an evil demon directly feeding the experiences to us.

Nevertheless, the consequence is the same in either case: whether experiences arise in me uncaused, or whether they are directly produced by an evil demon, on either alternative there is no logical necessity that their content be linked in any particular way. Kant's response to this is that without the required linkage (in the absence of the spatial 'form') there can be no self. Even an all-powerful evil demon cannot create a 'self' if the very conditions for the possibility of a self are not realized.

This tells us something about the 'evil demon' idea, or indeed any hypothesis about the 'ultimate ground for experience'. So far as the refutation of idealism is concerned, it makes absolutely no difference whether you assume an ultimate ground or not. The only thing that is required is that experience take a spatio-temporal 'form'.

In other words, so far as this argument is concerned, any reference to noumena or to how things stand in noumenal reality is otiose: irrelevant and besides the point.

Yet, clearly, this was not Kant's view! Like Descartes, he never once considers the possibility that 'this experience', whatever its form, say spatio-temporal, is 'all there is'.

This is a point on which there has been a significant amount of dispute. Did Kant think that the argument from the refutation of idealism, taken as it stands, is somehow sufficient to establish the existence of a noumenal reality? Is our very notion of an object somehow bound up with the idea that objects of perception have two aspects, the way they exist 'for us' (as spatio-temporal entities) and the way they are 'in themselves'? Are we indeed talking merely about two 'aspects' or two entirely separate realms of existence, the realm of our possible experience and the realm of 'things in themselves'?

And what about the 'dogmatic idealist'? Kant has in mind Berkeley, whose theory of immaterialism is almost indistinguishable from Descartes' evil demon hypothesis. I think that Kant could be accused of misunderstanding Berkeley, however, given that Berkeley never denies the meaningfulness of spatial concepts. Rather, what he rejects is the idea that we have a notion of 'matter' independent of our idea of perception. This is Kant's position too. The only difference between Berkeley and Kant seems to be that whereas Berkeley believes that it is possible to describe the ultimate ground of experience ('ideas in the mind of God') for Kant such talk goes beyond the bounds of metaphysical inquiry.

All the best,


Personal identity and exchanging bodies

To: Max W.
From: Geoffrey Klempner
Subject: Personal identity and exchanging bodies
Date: 5th November 2010 12:04

Dear Max,

Thank you for your email of 27 October, with the corrected version of your essay for the University of London Diploma Introduction to Philosophy module, in response to the question, 'Do you think it possible that one person could exchange bodies with another? Relate your answers to Locke or Williams or both.'

Let's start with aspects of the problem which don't really get to the core of the question. You note the practical difficulty involved in exchanging bodies, on the assumption that there is a material basis to consciousness. We know that much more than just a functioning brain is involved. It is indeed very likely that the very idea of removing a brain and putting it in another body is a science fiction fantasy which bears no relation to the scientific facts. (The same applies to thought experiments like the 'brain in a vat'.) The brain doesn't have a 3-pin connection (or even a 3000-pin connection) that you can just plug in to the spinal cord.

I think that it is worth noting this point, before moving on.

It wasn't clear to me that you had fully understood Locke's view of personal identity. Locke argues that the concept of a person is necessarily bound up with our notion of the criteria for personal identity. And, moreover, the concept of a person is 'forensic', in the sense that what concerns us is all that is necessary and sufficient for attributing personal responsibility, moral praise and blame etc. So sharply focused is his view of personal identity that he takes the extraordinary step of denying that the identity of a non-physical soul, whose presence we can never (ex hypothesi) detect is completely irrelevant to personal identity. If you and I switched souls, and your soul thereby acquired my memories and my soul acquired yours, then we would be totally unaware of the fact. It would be irrelevant to our respective identities as persons.

Locke is not committed to any particular view of what it is that accounts for consciousness and memory. He is simply reporting what anyone can observe for themself, that their sense of self is bound up with memory.

Consider the Prince and the cobbler, or, better still, the prima ballerina and the and the dying man. Make the difference between bodies and external circumstances as extreme as you like: we seem to be able to *imagine* what it would be like to wake up with a body that was not ours. What happened after that, the violent changes that this would wreak to our personalities is another question. Personal identity is consistent with even drastic change. As Locke would argue, so long as the thread of memory and consciousness remains, then the person is one and the same.

In any case, the question asked whether it is possible that one person could exchange bodies with another. If the answer is 'yes' in a few very restricted cases (say when we are dealing with twins, or persons whose bodies and physical abilities are similar) then it is yes. Even if it could be argued that it is not *always* possible to exchange bodies, it could still be the case that it sometimes is possible.

Questions relating to the self and the future, as opposed to the self and its memories, can be very confusing and Williams exploits this in his thought experiment of the anticipated torture. Suppose you are told that your memory and consciousness will be transplanted (say, by being uploaded onto disk then downloaded into a fresh brain), but that there will be two recipient brains, not one. The owner of the first brain will be tortured and the owner of the second will go on a luxury cruise. Can both the recipients be 'you'? Or, if not both, then one but not the other (only we don't know which)? How does one decide?

What this seems to show is that if we are prepared to go to the lengths of considering transplanting a 'person' into another body, what we would be giving up along the way is the last meaningful link to the idea of identity as opposed to mere similarity. The capacity to remember is a function, a property, which can be exemplified by more than one entity.

Insisting on the spatio-temporal continuity of that which is causally necessary and sufficient for continuity of memory and consciousness would be one way to resist the consequences of Locke's view. It does at least provide us with a criterion for 'true' memory as opposed to 'fake' memory (e.g. the person who 'remembers' being Marie Antoinette). But it won't do because the physical stuff itself -- brain stuff or whatever -- could in principle be divided any number of times between a corresponding number of new bodies.

One possible conclusion from this is that the very concept of a 'person' depends on particular empirical circumstances in such a way that, were those circumstances to change sufficiently, we could no longer have that concept. As Williams argues elsewhere, the name 'Max W' could become like 'Ford Capri', a general term or universal. When we imagine a person 'exchanging bodies with another' we wrongly assume that the concept of a 'person' is immutable, like a Cartesian soul substance that can be put here or put there. Whereas, if this happened in reality, persons as we know them would have ceased to exist.

All the best,


Monday, September 9, 2013

How thorough is Descartes' case for doubt?

To: Amru H.
From: Geoffrey Klempner
Subject: How thorough is Descartes' case for doubt?
Date: 2nd November 2010 12:07

Dear Amru,

Thank you for your email of 24 October, with your essay for the University of London Diploma Introduction to Philosophy module, in response to the question, ''I am finally compelled to admit that there is not one of my former beliefs about which a doubt may not properly be raised.' How does Descartes reach this conclusion? Are all his former beliefs undermined by the doubts he puts forward, or are some left untouched?'

I am glad to see that you are prepared to have a go at Descartes and find objections to his argument for the conclusion that 'there is not one of my former beliefs about which a doubt may not properly be raised.' Considering that this answer was written roughly within the one hour time limit you have not done too badly.

The first point I would make concerns what Descartes says about experience. On a first reading, it looks as though Descartes is trying several arguments against the reader: When the first one (the unreliability of some judgements based on perception) doesn't work, he ups the stakes and considers the dreaming hypothesis. When that doesn't fully achieve his purpose he ups the stakes again and considers the possibility of an evil demon.

Why not just go for the jugular straight away? All my experience could conceivably be the product of an evil demon, who has deliberately set out to persuade me of the existence of a world (Earth, say, in 2010). How do I know that this is not the case? And if I don't know for sure whether this world is real or an experience created in me by an evil demon, how can I possibly even estimate the probability that the world is real?

This looks as though it meets your objection that Descartes is wrongly assuming that nothing less than certainty would a sufficient basis for knowledge. He is talking about the foundations of knowledge. If the foundations were secure, then there would be no problem with judgements which are less than certain, because we would have a prior basis on which to estimate probabilities. But without a foundation, we are helpless. At least, that's the position he is arguing for.

The argument against the senses is important in its own right, because it establishes one very important principle: the possibility that a perceptual judgement may be false. What Descartes assumes, and this is a point you need to make more explicitly, is that whether or not my perceptual judgement (e.g. about a tower I see in the distance) is correct or not, there is something on the basis of which I make that judgement, the appearance of a tower, or its seeming to me to be the case that I see a tower. This certainty about my own mental states is assumed from the beginning and is one thing that survives all attempts at doubt, including the evil demon. In text books, you will see this described as the 'argument from illusion.'

The next step, is to make this explicitly in Meditation 2, by arguing that the judgement 'I exist' is necessarily true and immune from doubt.

Besides certainty about my own mental states, what else is left untouched by Descartes' arguments for scepticism? You mention Descartes' assumption (which unfortunately many of my students seem to ignore!) that he is sane. How is he to know? If you doubted whether you were sane, how could you possibly resolve that doubt? And yet Descartes happily sails over that problem. Is he right to do that? What could we say on his behalf if that assumption was challenged? 'This is an exercise in philosophy, and if I doubted my capacity for reason, then there wouldn't be any point in proceeding further.'

And yet he is prepared to consider the possibility that an evil demon could cause him to get simple arithmetical sums wrong. How are we to decide which aspects of 'reasoning' are beyond question -- which rational capacities define what it means to be 'sane' -- and which could conceivably be interfered with, without touching one's sanity?

You focus on Descartes' argument that there is no sure way of distinguishing dreams from reality. I suspect that you overstate the case here. Remember that Descartes is only using our familiar experience of dreaming as a starting off point. His argument is that there is nothing intrinsic to the quality of a dream experience which enables us to distinguish it from waking experience. Your argument about 'testing the sensed against the generally acquired experience' is in fact fully consistent with what Descartes says. Yes, that's what we do (if ever we are, on a rare occasion, seriously in doubt as to whether we are dreaming or not).

What Descartes is arguing, however, is that if there is nothing intrinsic to the quality of dream experience -- if we have to rely on general inductive considerations, as you argue, in order to distinguish dreams from reality -- then it is logically possible that all of my experience is a dream, or dream-like state. The 'Matrix' movies present a vivid picture of what this might be like. If I admit that it is logically possible that I am dreaming -- that it is logically possible, e.g. that 'the Matrix has me' -- then as before it's no use appealing to probabilities.

So I don't agree with your implication that Descartes' major error is setting the bar too high for knowledge. I'm not saying that he can't be criticized for over-simplifying this point. However, as I have indicated, if one grants the intelligibility of the evil demon hypothesis (a big 'if') then he has the means to defeat this objection, on the grounds that judgements of probability presuppose a prior certainty.

On the question of knowledge and certainty, you might be interested to read my answer to Demetrius, in the Ask a Philosopher pages:

All the best,


Parmenides on the unthinkability of 'what is not'

To Matthew M.
From: Geoffrey Klempner
Subject: Parmenides on the unthinkability of 'what is not'
Date: 29th October 2010 12:14

Dear Matthew,

Thank you for your email of 23 October, with your essay for the University of London BA Greek Philosophy: Presocratics and Plato module in response to the question, 'How important to Parmenides is his claim that "What is not" cannot be thought?'

You have had a good go at what seems to me a rather confusing question. There are various questions one could ask about Parmenides' One or 'What Is': What he means by 'is' (existence, predication, truth), the deductions which he draws from the premise 'It Is' (Reality has no past or future, no differentiation, is limited 'like a sphere' and so on).

You cover these in your essay; you also raise the very good question what Parmenides means by 'thought' or 'thinking': Does he have in mind a special kind of non-empirical thought, the thought that a God might think? You also make a good point about his use of 'not'. Surely, it cannot be that the very idea of negation is impossible, or in that case he could not coherently make the statement, 'What is not can not be thought.'

There is also a suggestion in your essay, which I would have liked to have seen expanded upon, that Parmenides was developing a critique of a particular way of thinking of 'what is not', as it were the reification of 'the not' as, e.g. the 'nothing' that (according to a certain naive way of thinking) separates one discrete object from another, or the idea of the universe coming into existence from a previous state of sheer non-being or non-existence, or indeed the idea that negation is a property alongside other properties (so that, e.g. in not being green, my table has the property of being brown and also the property of not-ness).

It would be nice if we could re-interpret Parmenides in this way, as offering critique of notions which undoubtedly deserve critique. That would rehabilitate his reputation in the eyes of contemporary philosophers. I have even come across an interpretation according to which 'what is' refers simply to 'the facts' or the 'totality of facts': as in the Tractatus, 'the world is all that is the case... facts in logical space' -- a space which is necessary filled and does not contain any gaps.

But this is taking us way off track.

What the question seems to be asking concerns Parmenides' motivations. The fact that some of the things he says -- applying the principle of charity -- could be interpreted in a way which makes him a lot more interesting in the eyes of contemporary philosophers is irrelevant.

I think that something you don't mention is relevant here. I does not seem implausible to see Parmenides as *reacting* to the nascent philosophical tradition, in particular the theories of the Milesians. All the talk about the Goddess, his seemingly half-hearted (but very thorough) pseudo-Milesian theory of 'light' and 'night' in the Way of Opinion, suggests that he is focusing on an idea in which he very much believes: the idea that there is a difference between appearance and reality, between how things present themselves to our senses and how reality presents itself to pure thought.

For Anaximenes, to take an example, the senses present a variety of kinds of substance arranged in various ways; what thinking discovers, by contrast, is one substance, air, all of whose modifications can be explained by a single process, condensation and rarefaction. In Parmenides' eyes, this is interesting but it is not fundamental. The theory arises out of thinking -- or more accurately speculating -- about the nature of reality, but it is still tied to the world of our senses.

Parmenides mind-blowing revelation is that thought alone, without any need to speculate or guess the ultimate nature of things, can determine how things really are in every relevant detail. It is logic alone which determines the nature of reality. What he is saying to the Milesians, effectively, is 'You can carry on doing what you do: here is my theory (the Way of opinion) to add to the debate. But you're missing something more fundamental.'

Note that I am not arguing the 'the One' is specifically intended to be the One of Milesian cosmology (which is an interpretation which has been offered alongside the other interpretations of the meaning of 'is'). If 'is' was intended to refer to the Milesian One, Parmenides' argument would be merely ad hominem. Whereas he is starting from the very basics, not assuming anything.

In that case, the answer to the question would be: What Parmenides means by thought is not thinking as a psychological phenomenon but rather as a logical notion. So that 'X cannot be thought' is equivalent to 'X is logically incoherent' or 'X is logically impossible'. The reason that the claim that 'What is not' cannot be thought is important, is that without any further premisses Parmenides is able, he thinks, to deduce the nature of reality, in all its logical features.

All the best,