Of Falsity
There is nothing positive in ideas which can constitute a form of falsity. But falsity cannot consist in absolute privation (for we say that minds and not bodies err and are mistaken); nor can it consist in absolute ignorance, for to be ignorant and to be in error are different. Falsehood, therefore, consists in the privation of knowledge which is involved by inadequate knowledge of things or by inadequate and confused ideas. For instance, men are deceived because they think themselves free, and the sole reason for thinking so is that they are conscious of their own actions, and ignorant of the causes by which those actions are determined. Their idea of liberty therefore is this—that they know no cause for their own actions; for as to saying that their actions depend upon their will, these are words to which no idea is attached. What the will is, and in what manner it moves the body, every one is ignorant, for those who pretend otherwise, and devise seats and dwelling-places of the soul, usually excite our laughter or disgust. Just in the same manner, when we look at the sun, we imagine its distance from us to be about 200 feet; the error not consisting solely in the imagination, but arising from our not knowing what the true distance is when we imagine, and what are the causes of our imagination. For although we may afterwards know that the sun is more than 600 diameters of the earth distant from us, we still imagine it near us, since we imagine it to be so near, not because we are ignorant of its true distance, but because a modification of our body involves the essence of the sun, in so far as our body itself is affected by it.
The Origin and Nature of Confused Ideas
The ideas of the modifications of the human body involve the nature both of external bodies and of the human body itself and must involve the nature not only of the human body, but of its parts, for the modifications are ways in which the parts of the human body, and consequently the whole body, are affected. But an adequate knowledge of external bodies and of the parts composing the human body does not exist in God in so far as He is considered as affected by the human mind, but in so far as He is affected by other ideas. These ideas of modifications, therefore, in so far as they are related to the human mind alone, are like conclusions without premises, that is to say, as is self-evident, they are confused ideas.
The idea which forms the nature of the mind is demonstrated in the same way not to be clear and distinct when considered in itself. So also with the idea of the human mind, and the ideas of the ideas of the modifications of the human body, in so far as they are related to the mind alone, as every one may easily see.
All ideas are in God and in so far as they are related to God are true and adequate. No ideas, therefore, are inadequate or confused unless in so far as they are related to the individual mind of some person. All ideas, therefore, both adequate and inadequate, follow by the same necessity.
The Origin and Nature of Adequate Ideas
Let there be something, A, which is common to all bodies, and which is equally in the part of each body and in the whole. I say that A can only be adequately conceived. For the idea of A will necessarily be adequate in God, both in so far as He has the idea of the human body and in so far as He has the idea of its modifications, which involve the nature of the human body, and partly also the nature of external bodies; that is to say, this idea will necessarily be adequate in God in so far as He constitutes the human mind, or in so far as He has ideas which are in the human mind. The mind, therefore, necessarily perceives A adequately, both in so far as it perceives itself or its own or any external body; nor can A be conceived in any other manner.
Hence it follows that some ideas or notions exist which are common to all men, for all bodies agree in some things, which must be adequately, that is to say, clearly and distinctly, perceived by all.
Hence it follows also that the more things the body has in common with other bodies, the more things will the mind be adapted to perceive.