“The generic concept of capital without which economists cannot do their work has no measurable counterpart among material objects; it reflects the entrepreneurial appraisal of such objects. Beer barrels and blast furnaces, harbour installations and hotel-room furniture are capital not by virtue of their physical properties but by virtue of their economic functions. Something is capital because the market, the consensus of entrepreneurial minds, regards it as capable of yielding an income. This does not mean that the phenomena of capital cannot be comprehended by clear and unambiguous concepts. The stock of capital used by society does not present a picture of chaos. Its arrangement is not arbitrary. There is some order in it.”