Catallactics is the praxeological theory of the way the market economy reaches exchange ratios and prices.

It aims to analyse all actions based on monetary calculation and trace the formation of prices back to the point where an economic actor makes his or her choices. It explains market prices as they are and not as they should be. The laws of catallactics are not value judgments, but aim to be exact, objective and of universal validity.

First used extensively by the Austrian economist Ludwig von Mises.