Wednesday, January 4, 2012

Can truth be defined?

To: Gordon F.
From: Geoffrey Klempner
Subject: Can truth be defined?
Date: 20 October 2006 10:20

Dear Gordon,

Thank you for your email of 13 October with your essay for units 7-9 of the Philosophy of Language program, in response to the question, 'Can truth be defined? - If you think that it can, give a definition and explain its philosophical significance. If you think that it cannot, what conclusions should the philosopher draw from that?'

In terms of comprehensiveness, the definitions of 'truth' and 'true' which you have cited are comparable to the entries in my 1973 copy of the 'Shorter Oxford English Dictionary'. It would be an interesting exercise to correlate them. (It is not inconceivable, given the similarity, that you have a newer edition of the SOED.) The resulting judgement would be that one or other of each definition is more accurate. One wouldn't speak of truth or falsity in this context, unless there was a flagrant misquotation or misattribution, or an incorrect etymology.

As your examples show, good dictionaries should show awareness of philosophical theory where appropriate. However, from the lexicographer's point of view, what philosophers say about 'truth', or 'justice', or 'person', or 'cause' is just more raw material for his/ her report (or, sometimes, recommendation) concerning accepted (or acceptable) usage.

You say in your essay that you have used the method of Dr Johnson and G.E. Moore to prove that '*truth* and *true* can be *defined*, in some sense of *definition*'. (You actually wrote, 'Berkeley' but I know you meant 'Dr Johnson, as it was he who kicked the stone. - this leads to an interesting question about truth: which statement of reported speech is 'true', the one which corrects your verbal slip, or the one which takes you at your precise word?)

However, that is the question at issue: we know already that true and truth can be 'defined' in a dictionary, as words which have usage in the language. The question is whether it is possible to give a philosophical definition.

That leads onto the question, what is a philosophical definition? Amongst analytic philosophers the word 'definition' has a generally accepted technical sense of 'necessary and sufficient conditions'. So, for example, a proposed definition of 'knowledge' would be:

A knows that P if and only if:

1. A believes that P
2. A is justified in believing that P
3. 'P' is true

This definition - if true - can be used to translate - in a non-trivial way - any piece of text which contains the word 'knows' into a piece of text which does not contain the word 'knows', just like any mathematical definition, e.g. the definition of 'equilateral triangle'. Debates over the proposed definition take the form of attempts at disproving the claim for either necessity or sufficiency by giving counterexamples - in the case of knowledge, Paul Gettier's paper, 'Is knowledge justified true belief?' is a notorious example.

So one sense of the essay question would be: can we do THIS with truth?

We can define 'a truth' as a statement/ proposition/ sentence/ judgement which is true (there is no circularity here because the next step is a definition of 'true'). We can pass on defining 'truth' without the substantive.

The next step is to simplify things further by deciding on the 'primary bearer of truth', i.e. what kinds of entities we defining the predicate 'true' over. There is considerable debate about this. One view is that 'true' applies primarily to sentences of a language, that is to say, our definition in terms of necessary and sufficient conditions applies to true and false sentences. But this is getting picky and technical. The big question is, Can this be done? Can the predicate 'true' be defined, non-trivially, in terms of necessary and sufficient conditions?

This is the point where one would consider the various definitions that have been proposed - in terms of correspondence, coherence, practical consequences etc.

Frege, in his paper 'The Thought: A Logical Inquiry' offers a knock-down argument directed at any attempt to define 'true'. The problem is, having given your definition, it then has to be applied to itself. If you say that a proposition is true if and only if it is X, you still have to give the truth conditions for 'being X' or 'not being X', sending you on a vicious regress.

That's one problem. But a larger problem, which your essay strongly hints at, is whether this exercise doesn't miss the point. Maybe philosophers can learn from a closer attention to lexicography. Is it irrelevant, as many analytic philosophers would claim, that an important use of the notion of truth is in the context where we are talking of a person's truthfulness, or being true to someone? (The British philosopher Bernard Williams has written on this, see http://www.pupress.princeton.edu/titles/7328.html for details of his book, 'Truth and Truthfulness'.)

I would like, ideally, to be able to explain ALL the commonly accepted uses of 'truth' and 'true' philosophically, in terms of a core philosophical definition of truth. The definition I would propose is the simplest of all the definitions: You can say that 'P' is true whenever you can say that P. 'True' is the only predicate that you can say this of (that's what makes the definition interesting and not at all trivial).

However, this merely restates the question: accepting that any definition of truth must have the consequence that you can say that 'P' is true whenever you can say that P (this is a simple statement of Tarski's Convention T, in his famous paper on 'The concept of truth in formalized languages'), can we, in fact give a more substantial account?

This needn't be in terms of necessary and sufficient conditions for truth. However, something does urgently need to be said about the POINT of truth. Why are we interested in it? So what, if there is a predicate which applies to any sentence P if and only if you can say P?

Michael Dummett, in his seminal paper 'Truth' (reprinted in 'Truth and Other Enigmas') argues that any philosophical account of truth must explain why truth is something at which we AIM.

As I said, I would like to think that this account of the point of our 'simple' definition of truth could be used to explain, and ultimately justify, all the uses noted in the dictionary. True North, for example, is what is North rather than where the compass needle points. A true friend is someone who is a friend, rather than someone who pretends to be one or who lets you down when the going gets tough, and so on.

All the best,

Geoffrey