“In the past fifty years the clearest manifestation of the tendency to think of the methods of ‘rational justification’ as given by something like a list or canon (although one that philosophers of science have admittedly not yet succeeded in fully formalizing) was the movement known as Logical Positivism. Not only was the list or canon that the positivists hoped ‘logicians of science’ (their term for philosophers) would one day succeed in writing down supposed to exhaustively describe the ‘scientific method’; but, since, according to the logical positivists, the ‘scientific method’ exhausts rationality itself, and testability by that method exhausts meaninfullness (‘The meaning of a sentence is its method of verification’), the list or canon would determine what is and what is not a cognitively meaningful statement. Statements testable by the methods in the list (the methods of mathematics, logic, and the empirical sciences) would count as meaningful; all other statements, the positivists maintained, are ‘pseudo-statements’, or disguised nonsense.

An obvious rejoinder was to say that the Logical Positivist criterion of significance was self refuting: for the criterion itself is neither (a) ‘analytic’ (a term used by the positivists to account for logic and mathematics), nor (b) empirically testable. Strangely enough this criticism had very little impact on the logical positivists and did little to impede the growth of their movement. I believe that the neglect of this particular philosophical gambit was a great mistake; that the gambit is not only correct, but contains a deep lessos, and not just a lesson about Logical Positivism.

[…] In sum, what the logical positivists and Wittgenstein (and perhaps the later Quine as well) did was to produce philosophies which leave no room for a rational activity of philosophy. This is why these views are self-refuting; and also why the little gambit I have been discussing represents a significant argument of the kind philosophers call a ‘transcendental argument’: arguing about the nature of rationality (the task of the philosophers par excellence) is an activity that presupposes a notion of rational justification wider than the positivist notion, indeed wider than institutionalized criterial rationality.”

PUTNAM, H. Reason, Truth and History, pp. 106; 113.