The a priori knowledge of praxeology is entirely different—categorially different—from the a priori knowledge of mathematics or, more precisely, from mathematical a priori knowledge as interpreted by logical positivism. The starting point of all praxeological thinking is not arbitrarily chosen axioms, but a self-evident proposition, fully, clearly and necessarily present in every human mind. An unbridgeable gulf separates those animals in whose minds this cognition is present from those in whose minds it is not fully and clearly present. Only to the former is the appellation man accorded.

Epistemology deals with the mental phenomena of human life, with man as he thinks and acts. The main deficiency of traditional epistemological attempts is to be seen in their neglect of the praxeological aspects. The epistemologists dealt with thinking as if it were a separate field cut off from other manifestations of human endeavor. They dealt with the problems of logic and mathematics, but they failed to see the practical aspects of thinking, They ignored the praxeological a priori.

The study of economics has been again and again led astray by the vain idea that economics must proceed according to the pattern of other sciences. The mischief done by such misconstructions cannot be avoided by admonishing the economist to stop casting longing glances upon other fields of knowledge or even to ignore them entirely. Ignorance, whatever subject it may concern, is in no case a quality that could be useful in the search for truth.

The republication of The Ultimate Foundation of Economic Science after a lapse of fifteen years must be judged a highly encouraging event — on the one hand, reflecting a welcome renewed interest in the subject and approach of the book itself and, on the other hand, holding forth promise of adding significantly to the current intellectual momentum toward a deeper understanding of the nature of economics and of its role in social betterment.

This essay is not a contribution to philosophy. It is merely the exposition of certain ideas that attempts to deal with the theory of knowledge ought to take into full account.