Theory is an abstract formulation of the constant relations between entities or, what means the same thing, the necessary regularity in the concatenation and sequence of phenomena and/or events. A theory may be true or false. A valid theory attempts to eliminate all contradictions in the application of cause and effect to a given specific situation or set of conditions. The aim of a theory is always success in action. A characteristic of a true theory is that action based on it succeeds in attaining the expected results. A theory is implicit in every human action and likewise a theory necessarily precedes the determination of "facts" and the writing of all history as well as the interpretation of every experience.
- Percy L. Greaves, Jr. "Mises Made Easier ", 1974. Referenced 2014-08-24.