Many years ago, in “The Communist Road to Self-Enslavement” (included in After the Open Society, a collection of Karl Popper’s papers edited by Jeremy Shearmur), I discovered the following sentence: “Like myself, [Ludwig von Mises] appreciated that there was some common ground, and he knew that I had accepted his most fundamental theorems and that I greatly admired him for these.”
As I respect both Popper and Mises as great thinkers, although thinkers who had differences, I was surprised. To be sure, in the paragraph containing the above sentence, Popper does discuss their differences, and then there is Mises’s disagreement with Popper in The Ultimate Foundation of Economic Science, where he writes in bold language,
If one accepts the terminology of logical positivism and especially also that of Popper, a theory of hypothesis is “unscientific” if in principle it cannot be refuted by experience. Consequently, all a priori theories, including mathematics and praxeology, are “unscientific.” This is merely a verbal quibble. No serious man wastes his time in discussing such a terminological question. Praxeology and economics will retain their paramount significance for human life and action however people may classify and describe them.
But how was it that Mises “knew,” and what was this acceptance “of his most fundamental theorems?” No Popper or Austrian scholar I have queried, including Jeremy Shearmur, has been forthcoming with an answer. Most consider it an offhand remark of little or no significance, even though it was in the context of an address at the 1992 American Economic Association annual meeting. Perhaps the perception is that there is little to be gained and much to be lost if these two intellectual giants agreed.
Recently while working on another project, I happened to read in proximity of time the following two discussions of action. First, we have Mises in The Ultimate Foundation of Economic Science:
The very category or concept of action comprehends the concepts of means and ends, of preferring and putting aside, viz., of valuing, of success and failure, of profit and loss, of costs. As no action could be devised and ventured upon without definite ideas about the relation of cause and effect, teleology presupposes causality.
And then we have Popper, in his Medawar Lecture “A New Interpretation of Darwinism” included in Hans-Joachim Niemann’s book Karl Popper and the Two New Secrets of Life:
The strange thing is that teleology enters the world with adaptation. Organisms are problem-solvers. Organisms seek better conditions. All of these are thoroughly teleological terms. “Better conditions” introduce evaluation. And no doubt organisms value, organisms prefer, organisms like this or that better than something else. We cannot avoid all teleological terms, and we cannot avoid all anthropomorphic terms.
Although Popper is generalizing action beyond humans to all organisms, the two quotations bear a striking similarity, especially on the question of preference or valuing. Was this the acceptance Popper was talking about—the acceptance of the axiom of action?
There is little doubt that Popper struggled with natural selection and, possibly, other theories that appeared to be a priori; but he developed the concept of the metaphysical research program to overcome the “terminological question,” as Mises called it, and incorporate unfalsifiable theories into the framework of science. Once this problem was overcome, he may have reevaluated Austrian theory and come to accept the truth of Mises’s axiom.
We may never know for certain what Popper meant or how Mises came to know it, but I choose to think that these two men were divided largely by the meaning of words and that their intellectual descendants have chosen to continue a feud that is largely devoid of intellectual content. A rapprochement between the supporters of Popper and Mises could provide a powerful intellectual force in the battle of ideas.