First we need to understand praxeology. It is the study of human action logic. It is action logic that takes into account time and causality. It is logic action in the passage of time. The notable characteristics of praxeology are time and causality and human action.
What emerges from this reflection is the consideration of the difference between a priori and a posteriori reasoning. A priori is from cause to effect, is based on something known – such as natural law – and it is valid independently of observation. A posteriori is based upon actual observation or upon experimental data, starting there and working back to their causes. Speaking about the power of science and the power of appropriate methodology, Mises says: “What makes natural science possible is the power to experiment, what makes social science possible is the power to grasp or to comprehend the meaning of human action.” [Ludwig von Mises,Money, Method and the Market Process (Kluwer Academic Publishers, 1990), Ch. 1, Section III.]