Page:The wealth of nations, volume 1.djvu/20

10, of the more scientific doctrines developed in later times. The leading developments of political economy since Adam Smith's time have been (1) the classical economy expounded by Ricardo, Malthus, J. B. Say, James Mill, etc., which for a long time held almost undisputed possession of the field; (2) as a later development, what is known as the "vulgar economy," consisting of the attempts made by writers such as Wagner, Laveleye, Jevons, and Sidgwick, to modify the classical economy in such a way as to justify legislative interference with the unrestrained freedom of modern capitalist production; and (3) the socialistic economy of Karl Marx and his school.

Among the Greeks, where commerce (in the ancient sense of the word, implying the direct exchange of commodities) was considerably extended, are found the first germs of this as of all other sciences. Economic questions could hardly escape the notice of philosophers, least of all of those in the first rank. Accordingly we find Plato and Aristotle alluding to the more important matters connected with the exchange of wealth in a manner which shows considerable insight into the question. Its production, however, entered but slightly into their calculations. The institution of slavery, upon which ancient industry was based, could not fail to obscure the importance of this aspect of the subject. Plato, indeed, perceives that labor is the source of all wealth; but the conditions of his time prevented him from seeing in their true light the consequences of this doctrine. In the "Republic" he says: