"According to this point of view, knowledge is, so to speak, a by-product of production or of investment. In research, on the contrary, it can be said that knowledge is the primary product. The distinction between products and by-products is not important for ordinary goods, because in a competitive regime the marginal costs of the two must be equal. But since knowledge does not have the normal properties of an economic good, it is necessary to study each mode of its production."