second book he sets to work to show, in detail, how experience gives rise to various kinds of
ideas. Having rejected innate ideas, he says:
"Let us then suppose the mind to be, as we say, white paper, void of all characters, without any
ideas; how comes it to be furnished? Whence comes it by that vast store, which the busy and
boundless fancy of man has painted on it with an almost endless variety? Whence has it all the
materials of reason and knowledge? To this I answer in one word, from experience: in that all our
knowledge is founded, and from that it ultimately derives itself" (Book II, Ch. I, Sec. 2).
Our ideas are derived from two sources, (a) sensation, and (b) perception of the operation of our
own mind, which may be called "internal sense." Since we can only think by means of ideas, and
since all ideas come from experience, it is evident that none of our knowledge can antedate
experience.
Perception, he says, is "the first step and degree towards knowledge, and the inlet of all the
materials of it." This may seem, to a modern, almost a truism, since it has become part of educated
common sense, at least in English-speaking countries. But in his day the mind was supposed to
know all sorts of things a priori, and the complete dependence of knowledge upon perception,
which he proclaimed, was a new and revolutionary doctrine. 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 third book of the Essay deals with words, and is concerned, in the main, to show that what
metaphysicians present as knowledge about the world is purely verbal. Chapter III, "Of General
Terms," takes up an extreme nominalist position on the subject of universals. All things that exist
are particulars, but we can frame general ideas, such as "man," that are applicable to many
particulars, and to these general ideas we can give names. Their generality consists solely in the
fact that they are, or may be, applicable to a variety of particular things; in their own being, as
ideas in our minds, they are just as particular as everything else that exists.
Chapter VI of Book III, "Of the Names of Substances," is concerned to refute the scholastic
doctrine of essence. Things may have