These three--namely, images, words, and ideas--are by many persons either entirely confused together, or not distinguished with sufficient accuracy or care, and hence people are generally in ignorance, how absolutely necessary is a knowledge of this doctrine of the will, both for philosophic purposes and for the wise ordering of life.

Those who think that ideas consist in images which are formed in us by contact with external bodies, persuade themselves that the ideas of those things, whereof we can form no mental picture, are not ideas, but only figments, which we invent by the free decree of our will; they thus regard ideas as though they were inanimate pictures on a panel, and, filled with this misconception, do not see that an idea, inasmuch as it is an idea, involves an affirmation or negation.

Again, those who confuse words with ideas, or with the affirmation which an idea involves, think that they can wish something contrary to what they feel, affirm, or deny.

This misconception will easily be laid aside by one, who reflects on the nature of knowledge, and seeing that it in no wise involves the conception of extension, will therefore clearly understand, that an idea (being a mode of thinking) does not consist in the image of anything, nor in words.

The essence of words and images is put together by bodily motions, which in no wise involve the conception of thought.
These few words on this subject will suffice: I will therefore pass on to consider the objections, which may be raised against our doctrine.