ledge is, secondly what it is that can be known, and thirdly how it
can be known. More explicitly, it comprises the analysis of the
various modes of "cognition," including not only knowledge in the
strict sense but also such others as imagination or belief, the dis-
crimination of the various types of proposition which one may
claim to believe or know, the analysis of these propositions and of
the concepts which occur in them, and the critical examination of
the evidence which we may have for holding them. Now it is
characteristic of all the philosophers who figure in this volume that,
while they may differ in the accounts that they give of the nature
of sense experience, and still more in the inferences that they draw
from them, they all agree that unless it is validly based upon our
sense experience we can have no sufficient ground for maintaining
any proposition about a matter of fact. And it is for this reason
that they are given the title of Empiricists.

Locke's purpose, as he himself describes it in the first chapter of
his Essay, is "to enquire into the original, certainty, and extent of
human knowledge, together with the grounds and degrees of belief,
opinion and assent": and it is on the enquiry into the "original"
of our knowledge that he founds all the rest. He assumes that in
order to discover how far knowledge can reach, and in what way
anything that passes for knowledge can make its title good, it is
necessary first to determine what knowledge consists in; and he
thinks that the way to answer this question is to start by showing
how knowledge is obtained. What he does, in fact, is to treat
knowledge as if it were an article of manufacture; and so we find
him asking where the raw material comes from and how it is
worked up. It might be thought that there was a preliminary
question to be asked about the nature of the raw material, but to
Locke this presents no problem. Having given the name of "idea"
to "whatsoever is the object of the understanding when a man
thinks," he assumes without further ado that the raw material of
knowledge consists of ideas. His argument is then devoted to show-
ing how we originally come by our ideas, and what we can
subsequently make of them.

Locke's answer to the first of these questions is that all our ideas
without exception come to us from Experience. Experience may
take the form Sensation, which gives us such simple ideas as those
of "yellow . . . heat . . . soft . . . bitter, and all those which we
call sensible qualities," or of Reflection, which is "the perception

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