These are two different tasks. The difference can best be demonstrated in discussing the catallactic concept of the entrepreneur. In the imaginary construction of the evenly rotating economy there is no room left for entrepreneurial activity, because this construction eliminates any change of data that could affect prices. As soon as one abandons this assumption of rigidity of data, one finds that action must needs be affected by every change in the data. Thus the outcome of action is always uncertain.
Action is always speculation.
This is valid not only with regard to a market economy but no less for Robinson Crusoe, the imaginary isolated actor, and for the conditions of a socialist economy. In the imaginary construction of an evenly rotating system nobody is an entrepreneur and speculator. Economics, in speaking of entrepreneurs, has in view not men, but a definite function. In embodying this function in an imaginary figure, we resort to a methodological makeshift. In using this term one must never forget that every action is embedded in the flux of time and therefore involves a speculation.