The study of the history of civilisation has, in Condorcet's eyes, two uses. It enables us to establish the fact of Progress, and it should enable us to determine its direction in the future, and thereby to accelerate the rate of progression. By the facts of history and the arguments they suggest, he undertakes to show that nature has set no term to the process of improving human faculties, and that the advance towards perfection is limited only by the duration of the globe. The movement may vary in velocity, but it will never be retrograde so long as the earth occupies its present place in the cosmic system and the general laws of this system do not produce some catastrophe or change which would deprive the human race of the faculties and resources which it has hitherto possessed. There will be no relapse into barbarism. The guarantees against this danger are the discovery of true methods in the physical sciences, their application to the needs of men, the lines of communication which have been established among them, the great number of those who study them, and finally the art of printing. And if we are sure of the continuous progress of enlightenment, we may be sure of the continuous improvement of social conditions. It is possible to foresee events, if the general laws of social phenomena are known, and these laws can be inferred from the history of the past. By this statement Condorcet justifies his bold attempt to sketch his tenth period of human history which lies in the future; and announces the idea which was in the next generation to be worked out by Comte. But he cannot be said to have deduced himself any law of social development. His forecast of the future is based on the ideas and tendencies of his own age. [Footnote: It is interesting to notice that the ablest of medieval Arabic historians, Ibn Khaldun (fourteenth century), had claimed that if history is scientifically studied future events may be predicted.] Apart from scientific discoveries and the general diffusion of a knowledge of the laws of nature on which moral improvement depends, he includes in his prophetic vision the cessation of war and the realisation of the less familiar idea of the equality of the sexes. If he were alive to-day, he could point with triumph to the fact that of these far-reaching projects one is being accomplished in some of the most progressive countries and the other is looked upon as an attainable aim by statesmen who are not visionaries. The equality of the sexes was only a logical inference from the general doctrine of equality to which Condorcet's social theory is reducible. For him the goal of political progress is equality; equality is to be the aim of social effort--the ideal of the Revolution.