Meaning and the Moral Sciences (Routledge Revivals)

Hilary Putnam

• Editorial: Routledge
• Año: 2013
• ISBN:
  9781136961830
• Edición: 1
• Categoría: Philosophie
• Categoría: Geschichte & Theorie der Philosophie

First published in 1978, this reissue presents a seminal philosophical work by professor Putnam, in which he puts forward a conception of knowledge which makes ethics, practical knowledge and non-mathematic parts of the social sciences just as much parts of 'knowledge' as the sciences themselves. He also rejects the idea that knowledge can be demarcated from non-knowledge by the fact that the former alone adheres to 'the scientific method'.

The first part of the book consists of Professor Putnam's John Locke lectures, delivered at the University of Oxford in 1976, offering a detailed examination of a 'physicalist' theory of reference against a background of the works of Tarski, Carnap, Popper, Hempel and Kant. The analysis then extends to notions of truth, the character of linguistic enquiry and social scientific enquiry in general, interconnecting with the great metaphysical problem of realism, the nature of language and reference, and the character of ourselves.

PART ONE
MEANING AND KNOWLEDGE

(The John Locke Lectures, 1976)

LECTURE I

The nature of truth is a very ancient problem in philosophy; but not until the present century did philosophers and logicians attempt to separate this problem from the problems of the nature of knowledge and the nature of warranted belief. That one could have a theory of truth which is neutral with respect to epistemological questions, and even with respect to the great metaphysical issue of realism versus idealism, would have seemed preposterous to a nineteenth-century philosopher. Yet that is just what the most prestigious theory of truth, Tarski’s theory,¹ claims to be.

Although it requires a certain amount of sophisticated logic to present this theory properly, one of the leading ideas, the idea of ‘disquotation’, is easy to explain. Take any sentence – say, Snow is white. Put quotation marks around that sentence – thus:

‘Snow is white.’

Now adjoin the words ‘is true’ – thus:

‘Snow is white’ is true.

The resulting sentence is itself one which is true if and only if the original sentence is true. It is, moreover, assertible if and only if the original sentence is assertible; it is probable to degree r if and only if the original sentence is probable to degree r; etc. According to Tarski, Carnap, Quine, Ayer, and similar theorists, knowing these facts is the key to understanding the words ‘is true’. In short, to understand P is true, where P is a sentence in quotes, just ‘disquote’ P – take off the quotation marks (and erase ‘is true’).

E.g. what does

‘Snow is white’ is true

mean? It means

Snow is white

What does

‘There is a real external world’ is true

mean? It means

There is a real external world

And so on.

The claim that ‘disquotation’ theorists are advancing is that an answer to the question what does it mean to say that something is true need not commit itself to a view about what that something in turn means or about how that something is or is not to be verified. You can have a materialist interpretation of ‘Snow is white’; you can believe ‘Snow is white’ is verifiable, or that it is only falsifiable but not verifiable; or that it is only confirmable to a degree between zero and one; or none of the foregoing; but ‘Snow is white’ is still equi-assertible with ‘”Snow is white” is true’. On this view, ‘true’ is, amazingly, a philosophically neutral notion. ‘True’ is just a device for ‘semantic ascent’ – for ‘raising’ assertions from the ‘object language’ to the ‘meta-language’, and the device does not commit one epistemologically or metaphysically.

I shall now sketch the second leading idea of Tarski’s theory. ‘True’ is a predicate of sentences in Tarski’s theory; and these sentences have to be in some formalized language L, if the theory is to be made precise. (How to extend the theory to natural languages is today a great topic of concern among philosophers and linguists.) Now a ‘language’ in this sense has a finite number of undefined or ‘primitive’ predicates. For simplicity, let us suppose our language L has only two primitive predicates – ‘is the moon’ and ‘is blue’. For predicates P, the locution

P refers to x

whose intimate connection with the word ‘true’ can be brought out by using the phrase ‘is true of’ instead of ‘refers to’, thus:

P is true of x

can also be explained by employing the idea of disquotation: if P is the predicate ‘is the moon’ we have:

‘Is the moon’ refers to x if and only if is the moon.

And if P is the predicate ‘is blue’ we have:

‘Is blue’ refers to x if and only if x is blue.

So the ‘meta-linguistic’ predication:

‘Is the moon’ refers to x

is equivalent to the ‘object-language’ predication:

x is the moon

Let us say P primitively refers to x if P is a primitive predicate (in the case of our language L, ‘is the moon’ or ‘is blue’) and P refers to x. Then primitive reference can be defined for our particular example L by giving a list:

Definition:

P primitively refers to x if and only if (1) P is the phrase ‘is the moon’ and x is the moon, or (2) P is the phrase ‘is blue’ and x is blue.

And for any particular formalized language a similar definition of primitive reference can be given, once we have been given a list of the primitive predicates of that language.

The rest of Tarski’s idea requires logic and mathematics to explain properly. I shall be very sketchy now.

The non-primitive predicates of a language are built up out of primitive ones by various devices – truth functions and quantifiers. Suppose, for the sake of an example, that the only devices are disjunction and negation: forming the predicates ‘P or Q’, and ‘not-P’ from the predicate P. Then we define reference as follows:

(I) If P contains zero logical connectives, P refers to x if and only if P primitively refers to x.

(II) P or Q refers to x if P refers to x or Q refers to x.

(III) Not-P refers to x if P does not refer to x.

Turning this inductive definition² into a proper definition is where much of the technical logic comes in; suffice it to say this can be done. The result is a definition of ‘reference’ for a particular language – a definition which uses no semantical words (no words in the same family as ‘true’ and ‘refers’).

Finally, supposing that our simple language is so simple³ that all sentences are of the forms for every x, Px, for some x, Px, or truth-functions of these (where P is a predicate), then true would be defined as follows (of course, Tarski actually considered much richer languages):

(I) for every x, Px is true if and only if, for every x, P refers to x.

(II) for some x, Px is true if and only if, for some x, P refers to x.

(III) if p and q are sentences, p or q is true if p is true or q is true; and not-p is true if p is not true.

While I have left out the mathematics of Tarski’s work (how one turns an ‘inductive definition’ like the above into an ‘explicit’ definition of the form ‘something is true if and only if …’, where ‘true’ and ‘refers’ do not occur in ‘…’) and I have ignored the immense complications which arise when the language has relations – two-place (or three-place, etc.) predicates – I hope I have conveyed three ideas:

(1) ‘Truth’ and ‘reference’ are defined for one particular language at a time. We are not defining the relation ‘true in L’ for arbitrary L.

(2) Primitive reference is defined ‘by a list’; and reference and truth in general are defined by induction on the number of logical connectives in the predicate or sentence, starting with primitive reference.

(3) The ‘inductive’ definition by a system of clauses such as (I), (II), (III), (I’), (II’), (III’), can be turned into a bona fide ‘explicit definition’ by technical devices from logic.

As a check on the correctness of what has been done, it is easy to derive the following theorem from the definition of ‘true’:

‘For some x, x is the moon’ is true if and only if, for some x, x is the moon.

And in fact, one can derive from the definition of true that

(T) ‘P’ is true if and only if P

when the dummy letter ‘P’ is replaced by any sentence of our language L.

That this should be the case – that the above schema (T) be one all of whose instances are consequences of the definition of ‘true’ – is Tarski’s ‘Criterion of Adequacy’ (the famous ‘Criterion T’) for definitions of ‘is true’.

Notice that while the idea of disquotation may initially strike one as trivial, Tarski’s theory is obviously very non-trivial. The reason is that the idea of disquotation only tells us that the Criterion T is correct; but it does not tell us how to define ‘true’ so that the Criterion T will be satisfied. Nor does disquotation by itself enable us to eliminate ‘true’ from all the contexts in which it occurs. ‘ Snow is white’ is true is equivalent to Snow is white; but to what sentence not containing the word ‘true’ (or any other ‘semantical’ term) is the following sentence equivalent: If the premisses in an inference of the form p or not-p/:.q are both true in L the conclusion is also true in L? Tarski’s method gives us an equivalent for this sentence, and for other sentences in which ‘is true’ occurs with variables and quantifiers, and that is what disquotation by itself does not do.

There are many problems with Tarski’s theory which bothered me for a number of years. One problem, which does not seem to me to be too serious, is that ‘true’ is taken as a predicate of sentences (i.e. strings of written signs) – strictly speaking, what is being analysed is not ‘is true’, as a predicate of statements, but ‘expresses a true statement’. But I take it that, although it is contrary to ordinary usage to speak of sentences as true or false, this usage is perfectly clear, and also this amount of deviation from ordinary usage is probably inevitable in any reconstruction (e.g. the use of the word ‘statement’).⁴ A more important objection is that the theory does not allow for sentences which are neither true nor false (e.g. ‘The number of trees in Canada is even’), or sentences containing indexical words (such as ‘now’, ‘here’, T). In fact, the theory can only be applied in its canonical form to languages in which every predicate is well defined and non-indexical. It now seems to me that it can be modified to apply to languages of other sorts; but this is not the sort of problem I shall deal with in these lectures. I shall also not distinguish between Tarski’s original theory and a recent and very elegant variant proposed by Saul Kripke. The criticism I wish to deal with in detail – one with which I at one time agreed – is due to Hartry Field.⁵

Field concedes that Tarski did accomplish something of philosophical importance in showing how to define the semantical notions of reference and truth in terms of the semantical notion of primitive reference. But Tarski was wrong, Field contends, in thinking that he had philosophically clarified primitive reference. Here is the crucial paragraph from Field’s article:⁶

Now, it would have been easy for a chemist late in the last century, to have given a Valence definition’ of the following form:

(3) (∀E) (∀n) (E has valence n = E is potassium and n is + 1, or … or E is sulphur and n is − 2)

where in the blanks go a list of similar clauses, one for each element. But, though this is an extensionally correct definition of valence, it would not have been an acceptable reduction; and had it turned out that nothing else was possible – had all efforts to explain valence in terms of the structural properties of atoms proved futile scientists would have eventually had to decide either (a) to give up valence theory, or else (b) to replace the hypothesis of physicalism by another hypothesis (chemicalism?). It is part of scientific methodology to resist doing (a) as long as the notion of valence is serving the purposes for which it was designed (i.e., as long as it is proving useful in helping us characterize chemical compounds in terms of their valences). But the methodology is not to resist (a) and (b) by giving lists like (3); the methodology is to look for a real reduction. This is a methodology that has proved extremely fruitful in science, and I think we are giving up this fruitful methodology, unless we realize that we need to add theories of primitive reference to T₁ or T₂ if we are to establish the notion of truth as a physicalistically acceptable notion.

What Field contends is that the Tarski definition of primitive reference (in our example, P primitively refers to x if P is the phrase ‘is the moon’ and x is the moon or P is the phrase ‘is blue’ and x is blue)...