The design of writing a history of human civilisation was premature, and to have produced a survey of any durable value would have required the equipment of a Gibbon. Condorcet was not even as well equipped as Voltaire. [Footnote: But as he wrote without books the Sketch was a marvellous tour de force.] The significance of his Sketch lies in this, that towards the close of an intellectual movement it concentrated attention on the most important, though hitherto not the most prominent, idea which that movement had disseminated, and as it were officially announced human Progress as the leading problem that claimed the interest of mankind. With him Progress was associated intimately with particular eighteenth century doctrines, but these were not essential to it. It was a living idea; it survived the compromising theories which began to fall into discredit after the Revolution, and was explored from new points of view. Condorcet, however, wedded though his mind was to the untenable views of human nature current in his epoch and his circle, did not share the tendency of leading philosophers to regard history as an unprofitable record of folly and crime which it would be well to obliterate or forget. He recognised the interpretation of history as the key to human development, and this principle controlled subsequent speculations on Progress in France. 6. Cabanis, the physician, was Condorcet's literary executor, and a no less ardent believer in human perfectibility. Looking at life and man from his own special point of view, he saw in the study of the physical organism the key to the intellectual and moral improvement of the race. It is by knowledge of the relations between his physical states and moral states that man can attain happiness, through the enlargement of his faculties and the multiplication of enjoyments, and that he will be able to grasp, as it were, the infinite in his brief existence by realising the certainty of indefinite progress. His doctrine was a logical extension of the theories of Locke and Condillac. If our knowledge is wholly derived from sensations, our sensations depend on our sensory organs, and mind becomes a function of the nervous system.