II
The idea of a modification of the human body does not involve an adequate knowledge of the body itself, or, in other words, does not adequately express its nature, that is to say, it does not correspond adequately with the nature of the human mind, and therefore the idea of this idea does not adequately express the nature of the human mind, nor involve an adequate knowledge of it.
From this it is evident that the human mind, when it perceives things in the common order of Nature, has no adequate knowledge of itself nor of its own body, nor of external bodies, but only a confused and mutilated knowledge; for the mind does not know itself unless in so far as it perceives the ideas of the modifications of the body. Moreover, it does not perceive its body unless through those same ideas of the modifications by means of which alone it perceives external bodies. Therefore in so far as it possesses these ideas it possesses an adequate knowledge neither of itself, nor of its body, nor of external bodies, but merely a mutilated and confused knowledge.
I say expressly that the mind has no adequate knowledge of itself, nor of its body, nor of external bodies, but only a confused knowledge, as often as it perceives things in the common order of Nature, that is to say, as often as it is determined to the contemplation of this or that externally—namely, by a chance coincidence, and not as often as it is determined internally—for the reason that it contemplates several things at once, and is determined to understand in what they differ, agree, or oppose one another; for whenever it is internally disposed in this or in any other way, it then contemplates things clearly and distinctly.