self-evident and irresistible. I exist. The consciousness of my
existence is to me the assurance of my existence.

Had Descartes done no more than point out this fact he would have no
claim to notice here; and we are surprised to find many writers looking
upon this "_Cogito, ergo sum_" as constituting the great idea in his
system. Surely it is only a statement of universal experience--an
epigrammatic form given to the common-sense view of the matter. Any
clown would have told him that the assurance of his existence was his
consciousness of it; but the clown would not have stated it so well. He
would have said, "I know I exist, because I feel that I exist."

Descartes therefore made no discovery in pointing out this fact as an
irreversible certainty. The part it plays in his system is only that of
a starting-point. It makes consciousness the basis of all truth. There
is none other possible. Interrogate consciousness, and its clear replies
will be science. Here we have a new basis and a new philosophy
introduced. It was indeed but another shape of the old formula, "Know
thyself," so differently interpreted by Thales, Socrates, and the
Alexandrians; but it gave that formula a precise signification, a thing
it had before always wanted. Of little use could it be to tell man to
know himself. How is he to know himself? By looking inward? We all do
that. By examining the nature of his thoughts? That had been done
without success. By examining the process of his thoughts? That, too,
had been accomplished, and the logic of Aristotle was the result.

The formula needed a precise interpretation; and that interpretation
Descartes gave. Consciousness, said he, is the basis of all knowledge;
it is the only ground of absolute certainty. Whatever it distinctly
proclaims must be true. The process, then, is simple: examine your
consciousness, and its clear replies. Hence the vital portion of his
system lies in this axiom: All clear ideas are true: whatever is clearly
and distinctly conceived is true. This axiom he calls the foundation of
all science, the rule and measure of truth.

The next step to be taken was to determine the rules for the proper
detection of these ideas; and these rules he has laid down as follows:

1. Never accept anything as true but what is evidently so; to admit
nothing but what so clearly and distinctly presents itself as true that
there can be no reason to doubt it.

2. To divide every question into as many