Now in the early Victorian period in which Marx planned his theorizing, political economy ruled the educated world. Ruskin had still to attack the primary assumptions of that tyrannous and dogmatic edifice. The duller sort of educated people talked of the "immutable laws of political economy" in the blankest ignorance that the basis of everything in this so-called science was a plastic human convention. Humane impulses were checked, creative effort tried and condemned by these mystical formulæ. Political economy traded on the splendid achievements of physics and chemistry and pretended to an inexorable authority. Only a man of supreme intelligence and power, a man resolved to give his lifetime to the task, could afford in those days to combat the pretensions of the political economist; to deny that his categories presented scientific truth, and to cast that jargon aside. As for Marx, he saw fit to accept the verbal instruments of his time (albeit he bent them not a little in use), to accommodate himself to their spirit and to split and re-classify and re-define them at his need. So that he has become already difficult to follow, and his more specialized exponents among Socialists use terms that arouse no echoes in the contemporary mind. The days when Socialism need present its theories in terms of a science whose fundamental propositions it repudiates, are at an end. One hears less and less of "surplus value" now, as one hears less and less of McCulloch's Law of Wages. It may crop up in the inquiries of some intelligent mechanic seeking knowledge among the obsolescent accumulations of a public library, or it may for a moment be touched upon by some veteran teacher. But the time when social and economic science had to choose between debatable and inexpressive technicalities on the one hand or the stigma of empiricism on the other, is altogether past.