To: Kyriakos C.
From: Geoffrey Klempner
Subject: Can truth be defined?
Date: 9th November 2011 13:04

Dear Kyriakos,

Thank you for your email of 31 October, with your third essay for Possible World Machine in response to the question, 'Can truth be defined? If you think it can, give a definition and explain its philosophical significance. If you think that it cannot, what considerations should the philosopher draw from that?'

Heidegger makes much of the point that for the Greeks truth was 'aletheia', that which is 'unconcealed', brought into the light of day (I understand that 'lethe' can refer to forgetting or concealing). What does this imply? You make the point that for the Greeks, the actual word for 'truth' can be deciphered as a complex thought. It is not just a label.

One could say that 'truth is that which is unconcealed' is intended as a definition of truth. Something that shows itself, that remains in the open, which we will not permit to be lost (forgotten). Yet this already poses a problem. Because facts, as such, are never just 'in the open'. We investigate the world, sometimes with great patience and persistence, and an answer comes to our questions (the scientist 'puts questions to nature'). But this answer is an interpretation, a deduction or induction, a conclusion. It is not just 'something seen'. It is almost as if the Greeks defined their 'truth' or 'aletheia' in a way which makes the acquisition of truth well nigh impossible. All our patient striving merely takes us from A to B, and from B to C. We never get to the truth, as such.

Yet Parmenides, repeating the words of the Goddess, asks us to believe that he has attained the 'well-rounded truth', 'It is', is all one needs to say. The truth, the whole truth, is all that follows from this proposition, and everything else is illusion.

But why can't 'true' be a useful label? Let the Greeks have their 'aletheia' and let's just concentrate on whether the word we use, in everyday discourse, has a definition. You are the second student whose work I have responded to today. That's true. Adding the label 'true' doesn't add any information. If you didn't believe me in the first place then assuring you that what I say is true wouldn't convince you either. But maybe there are circumstances where the use of the label 'true' is useful and necessary.

Wittgenstein in the 'Philosophical Investigations' argues that 'agreement in judgements' is the necessary condition for the very existence of meaningful discourse (contradicting the principle he held in the 'Tractatus' that we cannot allow that 'whether a proposition has meaning depends on whether another proposition is true'). If truth depends on, or is defined in terms of 'agreement', how can one leave open (as one surely must) the possibility, however seemingly remote, that we are all wrong? 'Our' world is flat, say. That's the truth, so far as we are concerned.

I would regard this as a fatal problem if one were seeking to define truth in terms of agreement. However, I see no contradiction in asserting (in Kantian, transcendental style) that the possibility of truth depends on the possibility of agreement, without taking the further step of attempting a definition in these terms.

In the new Study Partners forum http://www.philosophypathways.com/bentham/forum/ I (or my alter ego) respond to a problem raised by my student Joao Magalhaes, regarding the need to refer to truth in order to define knowledge in the traditional way ('justified true belief'). Why not just say:

Joao knows that Mars is the 2nd planet from the Sun if and only if:

1. Joao believes that Mars is the 2nd planet from the sun.
2. Joao has good justification for this belief.
3. Mars is the 2nd planet from the sun.

Now, repeat for 1st, 3rd, 4th, etc.

Repeat for Mercury, Venus, Earth, etc.

Repeat for any other sentence you like, until you get bored.

Job done.

In formal terms, 'true' is a device for propositional quantification. Seen as a mere 'label' the term 'true' enables us to say things like, 'Everything Kyriakos says in his last email is true.' By saying this I am expressing my complete agreement with you. On the matters discussed, we both think the same way. Of course (it goes without saying) we could both be wrong. Maybe the earth is flat after all. But the point is that a definition of truth is not the same as a criterion of truth. A definition of truth doesn't have to give us any additional information (how could it?) about how to determine whether any given statement or proposition is true. It's just a label, a device, and a very useful one at that.

This position is known as 'minimalism about truth'. Another, older, term is the 'redundancy theory' (although there is some debate as to whether these two terms mean exactly the same thing). Some would regard this as equivalent to the rejection of the possibility that truth can be defined. I would prefer to call it a definition. It answers the question, 'What is truth?' in the only way that that question can be answered.

What about 'internal statements'? Wittgenstein's argument against a private language is considered by many to be decisive here, but it leaves a worrying gap (discussed in my article 'Truth and subjective knowledge' http://klempner.freeshell.org/articles/shap.html). Maybe there 'is' something else, something which the label 'true' can never capture, something which each of us 'has' yet cannot express in any language.

All the best,

Geoffrey