Cartesianism.—The ideas of Descartes had considerable influence among his contemporaries, and Cartesianism, as it was called, became fashionable in intellectual circles. It developed a tendency towards free enquiry and independent thought; and it was even more significant as an atmosphere than as a system of ideas. Though in this respect too, it was both important and vital; as we have observed, modern mechanical theories find their parent in Descartes.

Nor was it only, we may remark, among philosophers and men of science that Cartesian ideas were popular; they were accepted and elaborated by the religious thinkers who hoped to harmonise and humanise theology and science. Pascal, Bossuet and Fénelon, the finest minds in the French Church, were eager Cartesians.[5]

This aspect of the matter, i.e. the significance of Cartesianism for religion, we can for the present postpone.

Results so Far.—Successive breaches in the Scholastic system have now been noted. Copernicus had introduced a new astronomy, Galileo a new physics, Descartes (with the help of Harvey) a new physiology, and the beginnings of a new psychology.

Contributions of Hobbes.—The step that remained was taken by an Englishman, Thomas Hobbes (1588-1679), who attempted to provide a system of ethics and a theory of politics upon a purely naturalistic basis. Hobbes was a particularly energetic thinker. He worked out a psychology of the feelings, which reduced everything to the impulse of self-preservation and the instinct for power. Men were induced by these instincts to agree to certain rules of conduct, for the sake of expediency. Social life seems essential if men are to live together—the instinct of self-preservation demands it—and social life in turn demands certain renunciations: thus fidelity, gratitude, forbearance, justice, etc., must be practised.

Thus Hobbes attempted to banish all mysterious or obscure forces from morality, which was the characteristic and inevitable product of human nature and human circumstances. This way of looking at things seemed strange to all, and even revolting to some, of Hobbes' contemporaries. As the mystical powers of motion which the Scholastics had believed in were banished by the new physics and the new physiology, so the new psychology could allow of no mystical faculty which can decide in all problems of good and evil.

With Hobbes, then, a naturalistic view of the universe may be said to have been tolerably complete: it embraces physics, psychology, and ethics. There still remained, of course, a number of gaps in scientific knowledge, and consequently any philosophy based thereupon could not yet be regarded as secure. These gaps, however, as research proceeded and successive discoveries were made, tended to diminish both in size and quantity.

Newton.—The seventeenth and the early eighteenth centuries were fruitful in revelations of this kind, and natural knowledge steadily and even rapidly progressed. And one thinker, who may be regarded as a link between the seventeenth century and that which succeeded it, may now claim our attention.

The name of Newton (1642-1727) is as familiar to Englishmen as that of Shakespeare, and the discovery by him of the "law of gravitation" is one of those scraps of information which we acquire, and perhaps fail to understand, in early childhood.

Newton's scientific method is a no less important aspect of his work than its results. The Principia, in which he gave his discovery to the world, is "a model for all scientific investigations which has never been surpassed." It was, indeed, a brilliant application of the principle of inferring the unknown from the already known, without any dogmatic leaps in the dark. The principle with which he began was that what is true in the narrower spheres of experience (e.g. in the case of an apple falling) is true also in the wider spheres (e.g. in the movements of the celestial bodies). He then made a careful mathematical deduction of what would happen in the case of the planets, assuming that the laws of falling bodies on the earth were applicable to them also. And he concluded by showing that what would happen according to mathematics under this assumption actually does happen. The conclusion follows that the same force, i.e. "attraction," operates in both cases. It is no wonder that this final and successful operation was performed by Newton "in a state of excitement so great that he could hardly see his figures."