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.

No thinking and no acting would be possible to man if the universe were chaotic, i.e., if there were no regularity whatever in the succession and concatenation of events. In such a world of unlimited contingency nothing could be perceived but ceaseless kaleidoscopic change. There would be no possibility for man to expect anything. All experience would be merely historical, the record of what has happened in the past. No inference from past events to what might happen in the future would be permissible. Therefore man could not act.

Reasoning is necessarily always deductive. This was implicitly admitted by all the attempts to justify ampliative induction by demonstrating or proving its logical legitimacy, i.e., by providing a deductive interpretation of induction. The plight of empiricism consists precisely in its failure to explain satisfactorily how it is possible to infer from observed facts something concerning facts yet unobserved.

Empiricism proclaims that experience is the only source of human knowledge and rejects as a metaphysical prepossession the idea that all experience presupposes a priori categories. But starting from its empiricistic approach, it postulates the possibility of events that have never been experienced by any man.

Determinism must be clearly distinguished from materialism. Materialism declares that the only factors producing change are those that are accessible to investigation by the methods of the natural sciences. It does not necessarily deny the fact that human ideas, judgments of value, and volitions are real too and can produce definite changes. But as far as it does not deny this, it asserts that these “ideal” factors are the inevitable result of external events that necessarily beget in the bodily structure of men definite reactions.