Praxeology is a priori. All its theorems are products of deductive reasoning that starts from the category of action. The questions whether the judgments of praxeology are to be called analytic or synthetic and whether or not its procedure is to be qualified as “merely” tautological are of verbal interest only.

History in the broadest sense of the term is the totality of human experience. History is experience, and all experience is historical. History comprehends also all the experience of the natural sciences. What characterizes the natural sciences as such is the fact that they approach the material of experience with the category of a strict regularity in the succession of events. History in the narrower sense of the term, i.e., the totality of experience concerning human action, must not and does not refer to this category.

The environment in which man acts is shaped by natural events on the one hand and by human action on the other. The future for which he plans will be codetermined by the actions of people who are planning and acting like himself. If he wants to succeed, he must anticipate their conduct.

The characteristic feature of man is action. Man aims at changing some of the conditions of his environment in order to substitute a state of affairs that suits him better for another state that suits him less. All manifestations of life and behavior with regard to which man differs from all other beings and things known to him are instances of action and can be dealt with only from what we may call an activistic point of view. The study of man, as far as it is not biology, begins and ends with the study of human action.

What distinguishes the field of human action from the field of external events as investigated by the natural sciences is the category of finality. We do no know of any final causes operating in what we call nature. But we know that man aims at definite goals chosen. In the natural sciences we search after constant relations among various events. In dealing with human action we search after the ends the actor wants or wanted to attain and after the result that his action brought about or will bring about.

Valuing is man’s emotional reaction to the various states of his environment, both that of the external world and that of the physiological conditions of his own body. Man distinguishes between more and less desirable states, as the optimists may express it, or between greater and lesser evils, as the pessimists are prepared to say. He acts when he believes that action can result in substituting a more desirable state for a less desirable.

The aim of all brands of positivism is to silence the sciences of human action. For the sake of argument we may abstain from analyzing positivism’s contributions to the epistemology of the natural sciences both with regard to their originality and to their soundness. Neither do we have to dwell too long upon the motives that incited the positivist authors’ passionate attacks upon the “unscientific procedure” of economics and history.

There are two branches of the sciences of human action, praxeology on the one hand, history on the other hand.

One does not annul the cognitive significance of the a priori by qualifying it as tautological. A tautology must ex definitione be the tautology—restatement—of something said already previously. If we qualify Euclidian geometry as a hierarchical system of tautologies, we may say: The theorem of Pythagoras is tautological as it expresses merely something that is already implied in the definition of a right-angled triangle.