The World's Greatest Books [Volumes 1-15, 17-20]

When this record of facts, this "natural history," is completed, an attempt may then be made to discover, by a comparison of the various facts, the cause of the phenomena. Here it is of the utmost importance to bear in mind that all facts have not the same value. There are, as Bacon points out, twenty-seven species of facts, and he concludes that in any science where facts cannot be tested by experiment there can be no conclusive evidence.

Thus it will be seen that Bacon's method was a system of specific rules. He did not merely tell men to make observations and experiments; he taught them how observations and experiments ought to be made.

As Bacon was the father of modern science, so Réne Descartes was the father of modern philosophy. Born in 1596, and perplexed by the movement of scepticism produced by the Renaissance, the French thinker endeavoured to find some ground of certainty in the fact that he at least knew of his own existence. Hence his famous saying: Cogito, ergo sum—"I think, therefore I exist." Consciousness, said he, is the basis of all knowledge. The process then is simple: examine your consciousness, and its clear replies will be science. Hence the vital portion of his system lies in this axiom: "All clear ideas are true."

The fallacy in his system can be briefly exposed. Consciousness is, no doubt, the ultimate ground of certainty of existence for me. But though I am conscious of all that passes within myself, I am not conscious of what passes in anything not myself. All that I can possibly know of anything not myself lies in its effects upon me. Any other ideas I may have in regard to the outside world are founded only on inferences, and directly I leave the ground of consciousness for the region of inference my knowledge becomes questionable.

It was this defect in Cartesianism which Baruch Spinoza, the great Jewish thinker of Amsterdam, set out to rectify. Spinoza asked himself: What was the reality which lies beneath all appearance? We see everywhere transformations perishable and perishing, yet there must be something beneath which is imperishable and immutable. What is it? In Spinoza's view, the absolute existence is God. All that exists, exists in and by God. Taking the words of St. Paul, "In Him we live and move and have our being," as his motto, he undertook to trace the relations of the world to God and to man, and those of man to society.

To John Locke, born at Wrington, in Somerset, in 1632, the problem presented itself in another way. Instead of accepting the validity of clear ideas, as Descartes and Spinoza did, he adopted the Baconian method, and opened the inquiry into the origin and formation of ideas. Separating himself from the philosophers who held that the mind was capable of arriving at knowledge independent of experience, and from the sceptics who maintained that the senses were the only channels of information, he showed that ideas were derived from two sources—sensation and reflection.

He was succeeded by George Berkeley, Bishop of Cloyne, born at Kilcrin in Kilkenny, in 1684. He defeated the sceptics on their own ground. There is nothing in the world, he says, except our own sensations and ideas. In order to exist for us, things have to be perceived by the mind; therefore, everything, in order to exist, must exist in the mind of God. But when Berkeley had proved that matter was figment, David Hume, born in 1711, came forward and showed that mind was also an illusion. You know nothing of matter, said Berkeley; you have only perceptions and the ideas based thereon. You know nothing of mind, replied Hume; you have only a succession of sensations and ideas.