He was thus able to enunciate his law of universal gravitation: “Every body attracts every other with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them.” From this formula he was able to deduce everything in planetary theory: the motions of the planets and their satell

From Pythagoras (whether by way of Socrates or not) Plato derived the Orphic elements in his philosophy: the religious trend, the belief in immortality, the other-worldliness, the priestly tone, and all that is involved in the simile of the cave; also his respect for mathematics, and his intimate intermingling of intellect and mysticism. From Parme

“I had rather be mad than delighted,”

Plato, in the Theaetetus had set to work to refute the identification of knowledge with perception, and from his time onwards almost all philosophers, down to and including Descartes and Leibniz, had taught that much of our most valuable knowledge is not derived from experience. Locke’s thorough-going empiricism was therefore a bold innovation.

THE great pre-Socratic systems that we have been considering were confronted, in the latter half of the fifth century, by a sceptical movement, in which the most important figure was Protagoras, chief of the Sophists. The word “Sophist” had originally no bad connotation; it meant, as nearly as may be, what we mean by “professor.” A Sophist was a ma

The second part tells how men escape from these evils by combining into communities each subject to a central authority. This is represented as happening by means of a social contract. It is supposed that a number of people come together and agree to choose a sovereign, or a sovereign body, which shall exercise authority over them and put an end to

There remains, however, something that I cannot doubt: no demon, however cunning, could deceive me if I did not exist. I may have no body: this might be an illusion. But thought is different. “While I wanted to think everything false, it must necessarily be that I who thought was something; and remarking that this truth, I think, therefore I am, wa

Hume is thus led to the view that, when we say “A causes B,” we mean only that A and B are constantly conjoined in fact, not that there is some necessary connection between them. “We have no other notion of cause and effect, but that of certain objects, which have been always conjoined together. . . . We cannot penetrate into the reason of the conj

Meanwhile science as technique was building up in practical men a quite different outlook from any that was to be found among theoretical philosophers. Technique conferred a sense of power: man is now much less at the mercy of his environment than he was in former times. But the power conferred by technique is social, not individual; an average ind