AN INTRODUCTORY LECTURE ON P. OLI_TIC?L ECONOMY 629 that demand and supply always tend to equilibrium ? use terms which are but paraphrases of the mathematical language which is the mother-tongue of the calculus of maxim?. and rainimp. The advantage of employing that language might perhaps be com? pared to the advantage of studying the ancient philosophers in their native tongue. I do not mean that the mathematical method should form part of the curriculum, as we make Greek obligatory fo.r the students of philosophy. But may we not hope that the h?gher path will sometimes be pursued by those candidates who offer special subjects for examination. Still referring to the theoretical part of political economy, ! come to the question: What is the use of abstract theory: the positive, as distinguished from the controversial use which I have indicated as extensive and important? I hope that in academic circles it may be allowable not to construe use narrowly. There still is room for the studies which the Greeks attributed to theoretical science, as distinguished from practical sagacity, which Aristotle 2 characterized as wonderful, and hard to be attained to, and sublime, but not immediately useful, not directly applied to the service of humanity, Of this character are the higher generalizations of economics, whether expressed in words or symbols, in the language of Ricardo or of Jevons, Such is the theory of the dependence of value upon cost, of the adjus?men? of remuneration ?o efforts and sacrifices; like ?he surface of the sea a sluggish sea with viscous waveBslowly settling to equilibrium. Such is the theory of the extension of demand in the different directions of consumption to one and the same limit of satisfaction; like an imprisoned gas pressing equally at all points against its boundary. Such is the theory, less familiar and less easily imaged, which is formed by com- bining the conceptions of Jevons and of Ricardo? and deducing the whole system of values and ?emunerations from the single simple principle that each individual seeks (subject to given conditions) simultaneously to maximize the pleasures of con: sumption and minimize the unpleasantness of production. From these heights of speculation, as from a lofty mountain, may be obtained general views as to the directions in which practice trends. Such a general direction has been afforded by the Ricardian theory of the rent of land. Such a general Cf. Mill, P?/?w/p/es, book ii. ch. xv. p. 7; book iii. ch. iii. p. 2. Ethics, book vi. chap. viii. Cf. Sidgwick, Pdncit?les of Political Economy, book ii. ch. tinciples of Economics, 2nd ed. pp. 544, et passim. ii.; Marshall,
