?28 TH:E ECONOMIC JOURNAL by no means the worst sort of economists, that they have almost forgotten, or at least degraded, the older, and in some respects more important theory which connects value with sacrifice and 'labour. There is ever a danger that, as we press on to seize new conceptions, we should lose the positions which have been already won. Hence the history of theory is particularly instructive in political economy as in philosophy. History and literature, dialectics,. and all that the Greeks comprehensively called words, seem the best corrective of the narrow prejudices and deceptive associations which are sure to be contracted by those who have J?een confined to a single school or system. Words indeed in a literal sense require the attention of the economist as well as the philosopher. For there is in both spheres a danger of -double-meaning terms; a demand for discriminating definition. ?In fact it has been seriously proposed by one of our greatest ?thinkers both in philosophy and political economy to revive the Platonic search for definition as a mettiod of economic ino -vestigation. So cognate ?re the studies of political economy and literee humaniores. It must not however be understood that economics are alto- 'gether of the complexion of literature and the humanities.
There is a certain affinity between the mathematical physics and
-the one social science which is largely occupied with measurable ?'quantities. The nature of things which has involved the know- '.ledge of physics in the mysteries of mathematics has not wished the way of cultivating economics to be altogether free from that ?difficulty. ? In the memorable words of Malthus'Many of the questions both in morals and politics seem to be of the nature of the problems de maximis et minimis in fluxions.' ?- The differential calculus, the master-key of the physical sciences, -unlocks the treasure-chamber of the pure theory of economics. I do not deny that the refinements of pure theory may be reached ?by the use of ordinary language, su?cient circumlocution being employed; the treasure-chamber has a key of its own, but it is a cumbrous one. Nor do I attribute to the mathe-
matical picklock the intricacy of the wards which guard the more
recondite treasures of the higher physics. On the contrary, there is required but a little strengthening and filing of the instruments ?which are in common use. The well-known economists who say that the cost of labear is a function of three variables and ? ' Deus ipse colendi Haud facilem esse viam voluit.'--V?RO?L, Georgic i. ? Bonar's MaltI.?s, p. ?.25.
