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A long thread on the Critical Rationalist facebook page began by drawing on von Mises’s criticism of Popper in The Ultimate Foundation of Economic Science “he [von Mises] addressed the claim of Karl Popper that scientific propositions must be falsifiable. Although Popper was not a positivist, he intended his falsification criterion to separate scientific from non-scientific statements.”

That is not a helpful statement without providing an account of the problem situation which the positivists and Popper addressed. For the positivists, the use of the inductive method was a distinctive feature of science, but Popper considered that induction was logically incoherent. Instead, he was looking for a convention make a clear distinction between (a) theories that claimed to be scientific (due to their alleged basis on evidence) which are nevertheless not refutable and (b) theories that do lay themselves open to falsification (in principle).

As described in The Guide to The Logic of Scientific Discovery, he made a significant departure from the usual approaches to decide these matters, either by logical analysis or by observation of the way scientists work (the naturalistic approach). He articulated the “rules of the game” or “conventions” approach. This is closely related to his rejection of certainty as an aim of science . He introduced the theme of conjectural knowledge as a permanent feature of scientific theories and not a transient situation or a “bug” in a new theory, to be superseded by further investigation and “confirmation”.

His criterion of demarcation is a proposal for an agreement or convention. He noted that his convention will be rejected by people who think that science can generate a system of “absolutely certain, irrevocably true statements”.

The test for his proposals is to examine their logical consequences, and to explore their fertility in solving problems in the theory of knowledge and scientific investigation. Essentially, it is a test of practice and practical results.

One of the practical implications of Popper’s criterion is that it can be used early in an argument to discover where the various parties stand on the use of evidence in the debate. It also prompts scientist to be constantly mindful of the importance of testing, with all that implies for the design of experiments and the attitude adopted towards adverse findings.

Popper’s program was radically different from the positivists, a fact obscured by people who can only see Popper’s falsifiability criterion as a rival of the positivists criterion of MEANING (they royally confused the issue by taking up testability as a criterion of meaning, as though Popper was working on the same problem).

Part of the problem here is the great significance ascribed to Science in the wake of Newton, when Science gained the reputation for finding ultimate truths. Previously the terms science or scientific merely implied systematic investigation with a view to obtaining useful principles, and so there was the science of angling and every other thing.

Part of the power of Popper’s program was to get away from the hopeless quest of the positivists/empiricists for a criterion of meaning (or cognitive significance) and the attempt to save inductive logic. The falsifiability criterion had logical coherence which the verification criterion lacked, and although falsification could not be decisive in practice, it did have the practical effect of pointing up the need for more critical attention to conventions to guide scientific practice (hence the program charted by Ian Jarvie).

One more important point: the focus of critical discussion for Popper was/were the laws of science, expressed as universal generalizations. That is what makes the logic of testing so strong (compared with verification). I don’t understand how a pure logical analysis can demonstrate that both the verification criterion and the falsifiability criterion are worthless. What is the point of Popper’s demarcation principle, given the larger contours of his program? Where is the universal statement that is tested by the basic statement “there is a chair in this room”? Is it a universal statement of any interest in the real world of scientific investigation?

This is the original argument.

In point of fact, the criterion is worthless, since every statement comes out verifiable under it. Suppose that “p” is a non-controversially verifiable statement, e.g., “there is a chair in this room.” Let us take “q” to be a statement logical positivists reject as meaningless. A good example is one that Rudolf Carnap held up to ridicule when he called for an end to metaphysics. He cited the following from Martin Heidegger’s Being and Time (1927): “The not nothings itself.” I shall not attempt to explain this: one can see why Carnap presented it as a paradigm instance of a meaningless statement. Does the verification principle eliminate it? Surprisingly, it does not. From p, we deduce p or q. (This step is non-controversial.) Assuming that a logical consequence of a verifiable proposition is itself verifiable, (p or q) is verifiable. Further, if p is verifiable, then the negation of p is verifiable; this principle seems difficult to question. Now, consider this argument: p or q not -p ______ q

This argument is valid, and each of its premises is verifiable. Then, q is a logical consequence of verifiable propositions, and it, too, is verifiable. Clearly, if the verification criterion cannot eliminate “the not nothings itself,” it is not worth very much. A falsification criterion fairs no better. If p is falsifiable, then (p and q) is falsifiable. Once more, not-p should be falsifiable if p is, though Karl Popper has implausibly denied this. By an argument parallel with that for verification, we conclude that q is falsifiable. One might think that this is a mere trick, readily avoidable through slight modification of the principle. There have been many attempts to formulate a criterion that comes up with the “right” results, but so far all have failed to withstand criticism.

What is the “right result” or the criterion for a “right result”?

Looked at in the context of testing (universal) scientific theories, what is wrong with the principle of falsifiability in logic and in practice for working scientists? With scientifically relevant statements in place of the ps and qs in the argument above would the result still look like a knockdown victory over Popper’s arguments?