Lei de Say

 The most important economic law at the micro level is the Law of Comparative Advantage (horizontal and vertical divisions of labor).

The most important economic law at the macro level is Say’s Law (on the origin of purchasing power).

An Austrian student or thinker is characterized by the mastery of the implications of both for entrepreneurial, and monetary fields. The whole of the defense of an economically free society rests respectively on both for each sphere, even.

Please see image for the former and url for the latter:

https://mises.org/library/rehabilitation-says-law