The idea of the progress of knowledge had created the idea of social Progress and remained its foundation. It was therefore logical and inevitable that Condorcet should take advance in knowledge as the clew to the march of the human race. The history of civilisation is the history of enlightenment. Turgot had justified this axiom by formulating the cohesion of all modes of social activity. Condorcet insists on "the indissoluble union" between intellectual progress and that of liberty, virtue, and the respect for natural rights, and on the effect of science in the destruction of prejudice. All errors in politics and ethics have sprung, he asserts, from false ideas which are closely connected with errors in physics and ignorance of the laws of nature. And in the new doctrine of Progress he sees an instrument of enlightenment which is to give "the last blow to the tottering edifice of prejudices." It would not be useful to analyse Condorcet's sketch or dwell on his obsolete errors and the defects of his historical knowledge. His slight picture of the Middle Ages reflects the familiar view of all the eighteenth century philosophers. The only contribution to social amelioration which he can discover in a period of nearly a millennium is the abolition of domestic slavery. And so this period appears as an interruption of the onward march. His inability to appreciate the historical role of the Roman Empire exhibits more surprising ignorance and prejudice. But these particular defects are largely due to a fundamental error which runs through his whole book and was inherent in the social speculations of the Encyclopaedists. Condorcet, like all his circle, ignored the preponderant part which institutions have played in social development. So far as he considered them at all, he saw in them obstacles to the free play of human reason; not the spontaneous expression of a society corresponding to its needs or embodying its ideals, but rather machinery deliberately contrived for oppressing the masses and keeping them in chains. He did not see that if the Progress in which he believed is a reality, its possibility depends on the institutions and traditions which give to societies their stability. In the following generation, it would be pointed out that he fell into a manifest contradiction when he praised the relative perfection reached in some European countries in the eighteenth century, and at the same time condemned as eminently retrograde all the doctrines and institutions which had been previously in control. [Footnote: Comte. Cours de philosophie positive, iv. 228.] This error is closely connected with the other error, previously noticed, of conceiving man abstracted from his social environment and exercising his reason in vacuo. 5.