The mechanical arts, Turgot says, were preserved in the dark ages by the necessities of existence, and because 'it is impossible but that out of the crowd of artisans practising them, there should arise from time to time one of those men of genius who are found mingled with other men, as gold is found mingled with the earth of a mine.' Surely in the same way holy men arose, with keener feeling for the spiritual necessities of the time, and finer knowledge to train and fit the capacities of human nature to meet these needs, and make their satisfaction the basis for yet loftier standards and holier aspirations and nobler and more careful practice. The work of all such men deserved a place in an outline of the progressive forces of the human mind, as much as the work of those who invented bills of exchange, the art of musical notation, windmills, clocks, gunpowder, and all the other material instruments for multiplying the powers of man and the conveniences of life. Even if we give Turgot the benefit of the doubt whether he intended to describe more than the progress of the human intelligence, or the knowing part of the mind, the omission of the whole moral side is still a defect. For as he interprets knowledge to be the conformity of our ideas to facts, has there not been a clearly recognisable progress in the improved conformity of our ideas to the most momentous facts of all, the various circumstances of human action, its motives and consequences? No factor among the constituents of a progressive civilisation deserves more carefully to be taken into account, than the degree in which the current opinion and usage of a society recognise the comprehensiveness of moral obligation. More than upon anything else, does progress depend on the kinds of conduct which a community classifies as moral or immoral, and upon the wider or narrower inclusiveness within rigid ethical boundaries of what ought or ought not to be left open and indifferent. The conditions which create and modify these ethical regulations,--their law in a word,--form a department of the history of the human mind, which can be almost less readily dispensed with than any other. What sort of a history of Europe would that be, which should omit, for example, to consider the influence of the moral rigour of Calvinism upon the growth of the nations affected by it?