was incarcerated in the prison of the Inquisition, where, ten years afterwards, he died. Still science progressed, and was considerably aided by the rapid increase in the number of newspapers throughout Europe. In 1631 the _French Gazette_ was established, and, soon after, newspapers appeared in all important cities, much to the discomfiture of the Church, whose power was now more seriously imperilled than ever. Confidence was gradually becoming established, and Descartes dared, in 1680, to make an attempt to analyse the mind, declaring that the necessity of universal doubt was the only starting-point of all true philosophy. He was followed, six years later, by Newton, who published his “Principia,” in which he demonstrated the grand truth which has immortalised his name—viz., that all bodies attract each other with forces jointly proportionate to their masses, varying universally as the squares of their distances. Thus was established the great law of universal gravitation, which marks an epoch in the intellectual development of man. Owing to the constantly-recurring feuds between the Lutherans, Calvinists, and Catholics, this great discovery passed for a while almost unnoticed; but it soon became apparent that the final blow had been given to the old theory of divine intervention in the movements of the universe, and that learned men of all countries were rapidly embracing the Newtonian theory of irreversible laws. It was, however, now too late for the Church to interfere, for all classes were quickly becoming impressed with the grand theory of gravitation, which was destined for ever to remain the most wonderful discovery of man; and, although the clergy still continued to anathematise all scholars and scientists, the study of nature was pursued with rapidly-increasing enthusiasm, as though to make up for lost time. In 1690 Locke, the physician and philosopher, published his “Essay on the Human Understanding,” in which he declared all human knowledge to be the result of experience, thus entirely upsetting the old theory of intuition. Twenty years later Leibnitz published his work entitled “Theodicée,” in which he endeavoured to solve the difficult problem of existence of evil in the world under the moral government of Deity. These two rival philosophers soon became the leaders of philosophic thought in their respective countries; but barely thirty years had passed away before an iconoclast appeared, in the person of David Hume, who cut away the ground ruthlessly from beneath their feet. His “Treatise on Human Nature,” published in 1739, upset all the philosophical systems of the past, replacing them by the great theory of causation, which was soon accepted by every philosopher and scientist. Kant followed in 1781 with his “Critique of Pure Reason,” in which he submitted matter to analysis, and declared it to be possessed of inherent force.