There Is Great Confusion Over the Meaning of Capital

The use of the capital concept, or, more accurately, of the capital concepts, has been the source of infinite confusion, a "second confusion of tongues, a second Babel." "Our science cannot possibly concede the right to its students for all times to call ten or twelve  fundamentally different things by the same name."  Thus wrote Böhm-Bawerk in 1888. . . . The words of Carl Menger written half a
century ago are just as true to-day. "There are," he said, "as many different and equally confused ideas as to what is the nature of capital as there are authors." It is almost unbelievable that, many decades after the publication of Böhm-Bawerk's Positive Theory, we should have to recall these words not as a historical reminiscence but as relevant to the present day.

--Fritz Machlup, The Stock Market, Credit, and Capital Formation, trans. Vera C. Smith (London: William Hodge and Company, 1940), 8-9.