It must give us confidence in facing such a prospect to observe that at each remove from the first appearance of the idea of progress in the world man's use of the word has carried more meaning and, though sometimes quieter in tone, as in recent times, is better grounded in the facts of life and history. Such an advance in our conceptions took place after the Renascence. At the beginning of the seventeenth century, when the art and science of the ancient world had been recovered, the word and the idea of progress started on a fresh course of unexampled vigour. The lines were closer to those of the pre-Christian than of the Catholic world, but it would be by no means true to call them pagan. When Bacon and Descartes begin to sound the modern note of progress, they think primarily of an advance in the arts and sciences, but there is a spiritual and human side to their ideal which could not be really paralleled in classical thought. The Spirit of Man is now invoked, and this, not in the sense of an elite, the builders of the Greek State or the rulers of the Roman Empire, but of mankind as a whole. This is Christian, or perhaps we should say, Stoical-Christian. Thus Descartes tells us that he looks to science to furnish us ultimately with an art which will make us 'masters and possessors of nature ... and this not solely for the pleasure of enjoying with ease the good things of the world, but principally for the preservation and improvement of human health which is both the foundation of all other goods and the means of strengthening the spirit itself' ('Discours de la Methode'). It is significant that the two words Progress and Humanity come into use in their modern sense side by side. The latter is the basis and the ideal of the former. But the new thing which had come into the world at this point, and gives a fresh impulse and content to the idea of progress, is the development of science. The Greeks had founded it and, as we shall see in a later chapter, it was the recovery of the Greek thread which gave the moderns their clue. But no one before the sixteenth century, before the marvels revealed by Galileo's telescope and knit up by Newton's synthetic genius, could have conceived the visions of human regeneration by science which light up the pioneers of the seventeenth century and are the gospel of the eighteenth.