The long life of Thomas Hobbes covers almost the whole of the most critical period alike in the growth of modern science and in the development of the British Constitution. Born in the year of the Armada, Hobbes did not die until nine years before the great Revolution which finally determined the question whether the British Islands should be ruled constitutionally or absolutely. He lived through the Stuart attempt to convert England into an absolute monarchy, the Puritan revolution and great Civil War, the political and ecclesiastical experiments of the Long Parliament and of Cromwell, the restoration of the exiled line, and the beginnings of modern Whiggism and Nonconformity. Still more remarkable were the changes which came over the face of science during the same period. When Hobbes entered the University as a lad, the sham Aristotelianism of the Middle Ages was still officially taught in its lecture-rooms; before he died, mechanical science had been placed on a secure footing by Kepler, Galileo, and Descartes, the foundations of the scientific study of physiology and magnetism had been laid by Harvey and Gilbert, the Royal Society for experimental research into nature had been incorporated for more than a generation, analytical geometry had been created by Descartes, and the calculus by Leibniz and Newton, while it was only eight years after his death that the final exposition of the new mechanical conception of the universe was given by Newton's Principia. It is only natural that a philosopher who was also a keen observer of men and affairs, living through such a period of crisis, should have made the most daring of all attempts to base the whole of knowledge on the principles of mechanical materialism, and should also have become the creator of a purely naturalistic theory of ethics and sociology.