The revolutionary speculations on the social and moral condition of man which were the outstanding feature of the eighteenth century in France, and began about 1750, were the development of the intellectual movement of the seventeenth, which had changed the outlook of speculative thought. It was one continuous rationalistic movement. In the days of Racine and Perrault men had been complacently conscious of the enlightenment of the age in which they were living, and as time went on, this consciousness became stronger and acuter; it is a note of the age of Voltaire. In the last years of Louis XIV., and in the years which followed, the contrast between this mental enlightenment and the dark background--the social evils and miseries of the kingdom, the gross misgovernment and oppression--began to insinuate itself into men's minds. What was the value of the achievements of science, and the improvement of the arts of life, if life itself could not be ameliorated? Was not some radical reconstruction possible, in the social fabric, corresponding to the radical reconstruction inaugurated by Descartes in the principles of science and in the methods of thought? Year by year the obscurantism of the ruling powers became more glaring, and the most gifted thinkers, towards the middle of the century, began to concentrate their brains on the problems of social science and to turn the light of reason on the nature of man and the roots of society. They wrought with unscrupulous resolution and with far-reaching effects. With the extension of rationalism into the social domain, it came about naturally that the idea of intellectual progress was enlarged into the idea of the general Progress of man. The transition was easy. If it could be proved that social evils were due neither to innate and incorrigible disabilities of the human being nor to the nature of things, but simply to ignorance and prejudices, then the improvement of his state, and ultimately the attainment of felicity, would be only a matter of illuminating ignorance and removing errors, of increasing knowledge and diffusing light. The growth of the "universal human reason"--a Cartesian phrase, which had figured in the philosophy of Malebranche--must assure a happy destiny to humanity.