But this condition of opinion was changed by the revolutionary shock which impelled France, the normal centre of Western Europe, to apply itself to the task of social regeneration. A third term of comparison, that is to say the type on which modern society is being moulded, now presented itself; though it lay as yet in a distant and obscure future. Compared with the mediaeval system it was seen to be an advance as great as that which justified our ancestors of chivalrous times in asserting superiority to their predecessors of antiquity. Until the destruction of Catholic Feudalism became an overt fact, its effete remnants had concealed the political future, and the fact of continuous progress in society had always remained uncertain. Social phenomena have this peculiarity, that the object observed undergoes a process of development as well as and simultaneously with the observer. Now up to the time of the Revolution, political development, on which the principal argument for the theory of Progress must always be based, corresponded in its imperfection to the incapacity of the scientific spirit to frame the theory of it. A century ago, thinkers of the greatest eminence were unable to conceive of a really continuous progression; and Humanity, as they thought, was destined to move in circles or in oscillations. But under the influence of the Revolution a real sense of human development has arisen spontaneously and with more or less result, in minds of the most ordinary cast; first in France, and subsequently throughout the whole of Western Europe. In this respect the crisis has been most salutary; it has given us that mental courage as well as force without which the conception could never have arisen. It is the basis of social science and therefore of all Positive Philosophy; since it is only from the social aspect that Positive Philosophy admits of being viewed as a connected whole. Without the theory of Progress, the theory of Order, even supposing that it could be formed, would be inadequate as a basis for Sociology. It is essential that the two should be combined. The very fact that Progress, however viewed, is nothing but the development of Order, shows that Order cannot be fully manifested without Progress. The dependence of Positivism upon the French Revolution may now be understood more clearly. Nor was it by a merely fortuitous coincidence that by this time the introductory course of scientific knowledge by which the mind is prepared for Positivism should have been sufficiently completed.