Praxeology is the general theory of purposeful human action developed deductively by Ludwig von Mises. Its starting category is the acting person; it is not a psychological test, a moral programme or a calculation of Bitcoin’s future price.
A person chooses a means because they expect a desired change. Purposeful action therefore includes error: a poorly chosen means may fail. Rationality in this Misesian sense means neither omniscience nor an observer’s approval of the end. A reflex without choice belongs to a different analytical category. [Mises — Human Action, I]
If two uses cannot occur together, choosing one sets aside the other. For example, an hour repairing a computer cannot simultaneously be an hour spent walking. This illustration does not specify the monetary price of the forgone option; its significance depends on that person’s ends and opportunities. [Mises — Human Action, I]
Giving, resting or helping someone can be purposeful action just like selling. Analysing means and ends does not itself judge which ultimate end is morally right. That a person acts implies neither an instruction to maximize monetary profit nor a claim that every plan is sensible in ordinary language. [Mises — Human Action, I]
Mises distinguishes general formal relations from history’s concrete content. Deductive validity depends on its assumptions; a claim about a particular country or period also requires determining whether the conditions apply. His claim for a priori theory is a methodological position, not a reason to declare any economic story proven. [Mises — Human Action, II]
Catallactics studies exchange and market phenomena within the broader category of action. Moving to prices, money and production requires further concepts and actual institutional conditions. The category of choice alone therefore determines neither which currency will be accepted nor the price of a particular transaction. [Mises — Human Action, XIV]
In Economics and Knowledge (1937), Hayek distinguishes the pure logic of choice from claims about how people acquire knowledge and coordinate plans. Such claims about the actual process have empirical content. Affinity with the Austrian tradition therefore does not mean every author accepts an identical methodology or scope for deduction. [Hayek — Economics and Knowledge, 1937]
Describing purposeful action cannot reveal the next exchange rate, a crisis date or the exact response of thousands of buyers. Such a conclusion adds assumptions about technologies, expectations and circumstances. Distinguish an argument’s logical validity from the truth of those assumptions and the success of a particular forecast. [Mises — Human Action, II]
Protocol rules can be checked in code; holders’ motives, merchant acceptance and knowledge diffusion are different questions. A praxeological interpretation can organize an argument about choice but cannot replace evidence about those processes. Identify each claim’s assumption, inference and observation instead of treating the method’s name as proof. [Hayek — Economics and Knowledge, 1937] [Hayek — The Use of Knowledge in Society, 1945]
For the clearest picture, read this entry together with Human Action, Methodological Individualism, Catallactics, Austrian economics, Knowledge Problem. The reverse links also lead from Methodological Individualism, Human Action, Catallactics, Ludwig von Mises.