پاتنم ت 3

13. On Practice

Popper's mistake here is no small isolated failing. What Popper consistently fails to see is that practice is primary: ideas are not just an end in themselves (although they are partly an end in themselves), nor is the selection of ideas to 'criticize' just an end in itself. The primary importance of ideas is that they guide practice, that they structure whole forms of life. Scientific ideas guide practice in science, in technology, and sometimes in public and private life. We are concerned in science with trying to discover correct ideas: Popper to the contrary, this is not obscurantism but responsibility. We obtain our ideas-our correct ones, and many of our incorrect ones-by close study of the world. Popper denies that the accumulation of perceptual experience leads to theories: he is right that it does not lead to theories in a mechanical or algorithmic sense; but it does lead to theories in the sense that it is a regularity of methodological significance that (1) lack of experience with phenomena and with previous knowledge about phenomena decreases the probability  of correct ideas in a marked fashion; and

2. extensive experience increases the probability of correct, or partially correct, ideas in a marked fashion. There is no logic of discovery' -in that sense, there is no logic of testing, either; all the formal algorithms proposed for testing, by Carnap, by Popper, by Chomsky, etc., are, to speak impolitely, ridiculous; if you don't believe this, program a computer to employ one of these algorithms and see how well it does at testing theories! There are maxims for discovery and maxims for testing: the idea that correct ideas just come from the sky, while the methods for testing them are highly rigid and predetermined, is one of the worst legacies of the Vienna Circle.

But the correctness of an idea is not certified by the fact that it came from close and concrete study of the relevant aspects of the world; in this sense, Popper is right. We judge the correctness of our ideas by applying them and seeing if they succeed; in general, and in the long run, correct ideas lead to success, and ideas lead to failures where and insofar as they are incorrect. Failure to see the importance of practice leads directly to failure to see the importance of success.

Failure to see the primacy of practice also leads Popper to the idea of ·a sharp 'demarcation' between science, on the one hand, and political, philosophical,  and ethical ideas, on the other. This 'demarcation' is pernicious, in my view; fundamentally, it corresponds to Popper's separation of theory from practice, and his related separa­tion of the critical tendency in science from the explanatory tendency in science. Finally, the failure to see the primacy of practice leads Popper to some rather reac­tionary political conclusions. Marxists believe that there are laws of society; that these laws can be known; and that men can and should act on this knowledge. It is not my purpose here to argue that this Marxist view is correct, but surely any view that rules

 

 

this out a priori is reactionary. Yet this is precisely what Popper does-and in the name of an anti-a priori philosophy of knowledge!

In general, and in the long run, true ideas are the ones that succeed-how do we know this? This statement too is a statement about the world; a statement we have come to from experience of the world; and we believe in the practice to which this idea corresponds, and in the idea as informing that kind of practice, on the basis that we believe in any good idea-it has proved successful! In this sense 'induction is circular'. But of course it is! Induction has no deductive justification; induction is not deduction. Circular justifications need not be totally self-protecting nor need they be totally uninformative: 16 the past success of 'induction' increases our confidence in it, and its past failure tempers that confidence. The fact that a justification is circular only means that that justification has no power to serve as a reason, unless the person to whom it is given as a reason already has some propensity to accept the conclusion. We do have a propensity- an a priori propensity, if you like-to reason 'inductively', and the past success of 'induction' increases that propensity.

The method of testing ideas in practice and relying on the ones that prove success­ ful (for that is what 'induction' is) is not unjustified. That is an empirical statement. The method does not have a 'justification' -if by a justification is meant a proof from eternal and formal principles that justifies  reliance on the method. But then, nothing does-not even, in my opinion, pure mathematics and formal logic. Practice is primary.