Who Said It (Economic Man)?

The answer is Frank H. Knight, capo di tutti capi among freshwater economists--and in so many ways a far more subtle thinker than so many of his successors.   It's the opening paragraph of The Economic Organization (1933), famous in folklore as the default alternative to the textbook he never wrote.  Folklore has it that Knight's sketch formed the framework for early editions of Paul Samuelson's textbook.  For a discussion, go here.