Praxeology is the science of human action. Let us determine its epistemology.

A science can be either a priori or a posteriori, and either analytic or synthetic.

A priori means that the validity of its statements can be determined before an actual experience, while a posteriori requires an experience. Analytic means its validity does not depend on actual entities, contrary to synthetic. Mathematics is a priori analytic. History is a posteriori synthetic.

Praxeology must follow an a priori synthetic epistemology. An analytic approach is fallible, because it requires to provide a definition of man. What if the experience, then, contradicts the deductions? Either one changes theory, or one changes man.

Praxeology must be synthetic by referring man to the actual entity instead of an external definition of man, ensuring thereby its accuracy. How can one then deduce statements, if not by observation of the entity? Praxeology rests on this axiom:

Man acts.

Let us examine the validity of the axiom of human action. It can be false through 3 ways:

1. Man is false. Since it is a reference to a real entity, it is necessarily true.
2. Action in itself is false. Since action is composed from distinct true atomic concepts, there is no contradiction.
3. Man, by its nature, is contradictory with action. In that case, it would be contradictory with one of the atomic concepts of action. Since man is, even particularly, we can apply the same reasoning to what is generally.

Consequently, the axiom of human action cannot be wrong. More specifically, because of the noumenon-phenomenon correspondence, any deduction from the axiom cannot be proved wrong by any single actual fact.

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