The debate all stems from Mises’s confusion about basic epistemological concepts such as analyticity, a confusion identified by Hans Albert (1999: 131–132).
And this passage from Mises’s The Ultimate Foundation of Economic Science: An Essay on Method (1962) shows that his view of praxeology is indeed indebted to Kant:
“There are two branches of the sciences of human action, praxeology on the one hand, history on the other hand.For Mises, the human mind has Kantian a priori categories and presumably Kant’s two “pure forms of cognition/intuition” (namely, space and time).
Praxeology is a priori. It starts from the a priori category of action and develops out of it all that it contains. For practical reasons praxeology does not as a rule pay much attention to those problems that are of no use for the study of the reality of man’s action, but restricts its work to those problems that are necessary for the elucidation of what is going on in reality. Its intent is to deal with action taking place under conditions that acting man has to face. This does not alter the purely aprioristic character of praxeology. It merely circumscribes the field that the individual praxeologists customarily choose for their work. They refer to experience only in order to separate those problems that are of interest for the study of man as he really is and acts from other problems that offer a merely academic interest. The answer to the question whether or not definite theorems of praxeology apply to a definite problem of action depends on the establishment of the fact whether or not the special assumptions that characterize this theorem are of any value for the cognition of reality. To be sure, it does not depend on the answer to the question whether or not these assumptions correspond to the real state of affairs that the praxeologists want to investigate. The imaginary constructions that are the main—or, as some people would rather say, the only—mental tool of praxeology describe conditions that can never be present in the reality of action. Yet they are indispensable for conceiving what is going on in this reality. Even the most bigoted advocates of an empiricist interpretation of the methods of economics employ the imaginary construction of an evenly rotating economy (static equilibrium), although such a state of human affairs can never be realized.
Following in the wake of Kant’s analyses, philosophers raised the question: How can the human mind, by aprioristic thinking, deal with the reality of the external world? As far as praxeology is concerned, the answer is obvious. Both, a priori thinking and reasoning on the one hand and human action on the other, are manifestations of the human mind. The logical structure of the human mind creates the reality of action. Reason and action are congeneric and homogeneous, two aspects of the same phenomenon. In this sense we may apply to praxeology the dictum of Empedocles γνῶσις τοῦ ὁμοίου τῷ ὁμοίῳ.
Some authors have raised the rather shallow question how a praxeologist would react to an experience contradicting theorems of his aprioristic doctrine. The answer is: in the same way in which a mathematician will react to the ‘experience’ that there is no difference between two apples and seven apples or a logician to the ‘experience’ that A and non-A are identical. Experience concerning human action presupposes the category of human action and all that derives from it. If one does not refer to the system of the praxeological a priori, one must not and cannot talk of action, but merely of events that are to be described in terms of the natural sciences. Awareness of the problems with which the sciences of human action are concerned is conditioned by familiarity with the a priori categories of praxeology. Incidentally, we may also remark that any experience in the field of human action is specifically historical experience, i.e., the experience of complex phenomena, which can never falsify any theorem
in the way a laboratory experiment can do with regard to the statements of the natural sciences.” (Mises 1962: 41–42).
But for Kant humans could not know necessary truth of the true external world (what Kant called the “thing-in-itself” or the world of “noumena”). Rather, Kant thought that necessary and universal truth exists in the human world of the “objects of our experience” or the “phenomena,” or what modern philosophers might call the world of “sense data” in our minds. Nevertheless, this world of “phenomena” was “empirically real” for Kant (as well as “transcendentally ideal”). So Kantian synthetic a priori appears to be confined to the world of “phenomena,” not of the external world of “noumena”.
Mises dispenses with this, and thinks that human categories and a priori thought provide real knowledge of an external world (or what Kant called the “thing-in-itself”).
The trouble with Mises’s view is that Kant’s a priori “categories” and “pure forms,” to the extent that any of them exist, are innate biological and contingent traits of the human mind given to us by Darwinian evolution.
The modern discipline of “evolutionary epistemology” has shown convincingly that such traits are not epistemologically a priori:
“Konrad Lorenz [a evolutionary epistemologist] …. is famous for reinterpreting Kant’s synthetic a priori claims. No longer are the inborn categories regarded as evidently true, rather, they are understood to be “ontogenetically a priori and phylogenetically a posteriori.” This means that an individual organism is born with innate dispositions. These innate dispositions are acquired phylogenetically, through the evolution of the species, by means of the mechanism of natural selection. Most importantly, these dispositions are fallible, because they are the result of selection, not instruction. That is, these dispositions are adaptations, and natural selection only weeds out maladaptive organisms, which results in the survival of the adaptive ones. ….Nevertheless, human innate cognitive and psychological traits do not provide us with necessarily true and a priori knowledge of the external world: some of our mental traits and “categories” are partially isomorphic but others can be fallible and mistaken. Ultimately, they are all a posteriori and contingent.
According to Lorenz, and contrary to Kant, the thing in itself (Das Ding an Sich) is knowable through the categories of the knower, not the characteristics of the thing in itself, and selection results in a partial isomorphism through adaptation. …. Thus, through adaptation, there is a correspondence between our images of the world and the world in itself, or between organism and environment, or between theories and the world. This is of course not a 1-to-1 correspondence; our image of a tree is not like a real tree, but because our cognitive apparatus is adapted to the world, there is a partial isomorphism between the two. Adaptations thus become a description of the world in a biological language.”
Gontier, “Evolutionary Epistemology,” Internet Encyclopedia of Philosophy, 2006
A second point is that this passage above also shows that Mises rejects, and perhaps does not even understand, the distinction between (1) analytic a priori pure mathematics and geometry and (2) synthetic a posteriori applied mathematics and geometry.
And, for Mises, both mathematics and praxeology are a priori and also provide real necessary knowledge of reality. That entails that Mises saw these things as Kantian synthetic a priori knowledge.
Gontier, “Evolutionary Epistemology,” Internet Encyclopedia of Philosophy, 2006
“Evolutionary Epistemology,” Stanford Encyclopedia of Philosophy, 2001 (rev. 2012)
Albert, H. 1999. Between Social Science, Religion and Politics: Essays in Critical Rationalism. Rodopi, Amsterdam.
Mises, Ludwig von. 1962. The Ultimate Foundation of Economic Science: An Essay on Method. Van Nostrand, Princeton, N.J.