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say that a man assents to what is false and does not doubt it, we do not
say that he is certain, but merely that he does not doubt, that is to
say, that he assents to what is false, because there are no causes
sufficient to make his imagination waver. Although, therefore, a man may
be supposed to adhere to what is false, we shall never on that account
say that he is certain. For by certitude we understand something
positive, and not the privation of doubt; but by the privation of
certitude we understand falsity.

If the preceding proposition, however, is to be more clearly
comprehended, a word or two must be added; it yet remains also that I
should answer the objections which may be brought against our doctrine,
and finally, in order to remove all scruples, I have thought it worth
while to indicate some of its advantages. I say some, as the principal
advantages will be better understood later.

I begin, therefore, with the first, and I warn my readers carefully to
distinguish between an idea or conception of the mind and the images of
things formed by our imagination. Secondly, it is necessary that we
should distinguish between ideas and the words by which things are
signified. For it is because these three things, images, words, and
ideas, are by many people either altogether confounded or not
distinguished with sufficient accuracy and care that such ignorance
exists about this doctrine of the will, so necessary to be known both
for the purposes of speculation and for the wise government of life.
Those who think that ideas consist of images, which are formed in us by
meeting with external bodies, persuade themselves that those ideas of
things of which we can form no similar image are not ideas, but mere
fancies constructed by the free power of the will. They look upon ideas,
therefore, as dumb pictures on a tablet, and being prepossessed with
this prejudice, they do not see that an idea, in so far as it is an
idea, involves affirmation or negation. Again, those who confound words
with the idea, or with the affirmation itself which the idea involves,
think that they can will contrary to their perception, because they
affirm or deny something in words alone contrary to their perception. It
will be easy for us, however, to divest ourselves of these prejudices if
we attend to the nature of thought, which in no way involves the
conception of extension, and by doing this we clearly see that an idea,
since it is a mode of