far as that external body conditions the human body in a given manner. But, in so far as the external body is an individual, which has no reference to the human body, the knowledge or idea thereof is in God (II. ix.), in so far as God is regarded as affected by the idea of a further thing, which (II. vii.) is naturally prior to the said external body. Wherefore an adequate knowledge of the external body is not in God, in so far as he has the idea of the modification of the human body; in other words, the idea of the modification of the human body does not involve an adequate knowledge of the external body. Q.E.D.
PROP. XXVI. The human mind does not perceive any external body as actually existing, except through the ideas of the modifications of its own body.
Proof.—If the human body is in no way affected by a given external body, then (II. vii.) neither is the idea of the human body, in other words, the human mind, affected in any way by the idea of the existence of the said external body, nor does it in any manner perceive its existence. But, in so far as the human body is affected in any way by a given external body, thus far (II. xvi. and Coroll.) it perceives that external body. Q.E.D.
Corollary.—In so far as the human mind imagines an external body, it has not an adequate knowledge thereof.
Proof.—When the human mind regards external bodies through the ideas of the modifications of its own body, we say that it imagines (see II. xvii. note); now the mind can only imagine external bodies as actually existing. Therefore (by II. xxv.), in so far as the mind imagines external bodies, it has not an adequate knowledge of them. Q.E.D.
PROP. XXVII. The idea of each modification of the human body does not involve an adequate knowledge of the human body itself.
Proof.—Every idea of a modification of