John Stuart Mill, in that section of his _System of Logic_ to which he gives the title of “_The Logic of the Moral Sciences_,” writes thus. “_In the difficult process of observation and comparison which is required (for the purpose of obtaining a better understanding of the laws of empirical sociology, and especially of social progress) it would evidently be a great assistance if it should happen to be the fact that one element in the complex existence of social man is pre-eminent over all the others, as the prime agent {133} of the social movement. For we could then take the progress of that one element as the central chain, to each successive link of which, the corresponding links of all the other progressions being appended, the succession of facts would by this alone be presented in a kind of spontaneous order, far more approaching to the real order of their filiation than could be obtained by any other merely empirical process. Now the evidence of history and that of human nature combine, by a striking instance of consilience, to show that there really is one social element which is predominant and almost paramount amongst the agents of social progression. This is the state of the speculative faculties, including the nature of the beliefs which by any means they have arrived at, concerning themselves and the world by which they are surrounded. Thus_,” Mill continues, “_to take the most obvious case, the impelling force to most of the improvements effected in the arts of life is the desire for increased material comfort; but as we can only act on external objects in proportion to our knowledge of them, the state of knowledge at any given time is the limit of the industrial improvement possible at that time, and therefore the progress of industry must follow and depend upon the progress of that knowledge_.” Any one who was inclined to be hypercritical might object, and object with justice, that the practical application of knowledge often lags behind the speculative attainment, and that material progress therefore, at certain times, depends on {134} some new state of the practical rather than of the speculative faculties; but apart from this not very important inaccuracy of expression, Mill’s way of putting the case is admirable for its lucidity and for its truth; and we may, for our present purpose, be content to take it as it stands. All civilisation depends on the accumulation of speculative knowledge, and all progress in civilisation depends on an increase in speculative knowledge.