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. Those ideas are also adequate which follow in the mind from ideas which are adequate in it. For when we say that an idea follows in the human mind from ideas which are adequate in it, we do but say that in the divine intellect itself an idea exists of which God is the cause, not in so far as He is infinite, nor in so far as He is affected by the ideas of a multitude of individual things, but in so far only as He constitutes the essence of the human mind.