P35: Falsity consists in the privation of knowledge which inadequate, or mutilated and confused, ideas involve.

Dem.: There is nothing positive in ideas that constitutes the form of falsity (by P33); but falsity cannot consist in an absolute privation (for it is Minds, not Bodies, which are said to err, or be deceived), nor also in absolute ignorance. For to be ignorant and to err are different. So it consists in the privation of knowledge that inadequate knowledge of things, or inadequate and confused ideas, involve, q.e.d.

Schol.: In P17 S I explained how error consists in the privation of knowledge. But to explain the matter more fully, I shall give {NS: one or two examples}: men are deceived in that they think themselves free {NS: i.e., they think that, of their own free will, they can either do a thing or forbear doing it}, an opinion which consists only in this, that they are conscious of their actions and ignorant of the causes by which they are determined. This, then, is their idea of freedom—that they do not know any cause of their actions. They say, of course, that human actions depend on the will, but these are only words for which they have no idea. For all are ignorant of what the will is, and how it moves the Body; those who boast of something else, who feign seats and dwelling places of the soul, usually provoke either ridicule or disgust.

Similarly, when we look at the sun, we imagine it as about 200 feet away from us, an error that does not consist simply in this imagining, but in the fact that while we imagine it in this way, we are ignorant of its true distance and of the cause of this imagining. For even if we later come to know that it is more than 600 diameters of the earth away from us, we nevertheless imagine it as near. For we imagine the sun so near not because we do not know its true distance, but because an affection of our body involves the essence of the sun insofar as our body is affected by the sun.