Éthique, Partie V, Proposition 31

The mind does not conceive anything under the form of eternity, except in so far as it conceives its own body under the form of eternity (V. xxix.); that is, except in so far as it is eternal (V. xxi. xxiii.); therefore (by the last Prop.), in so far as it is eternal, it possesses the knowledge of God, which knowledge is necessarily adequate (II. xlvi.); hence the mind, in so far as it is eternal, is capable of knowing everything which can follow from this given knowledge of God (II. xl.), in other words, of knowing things by the third kind of knowledge (see Def. in II. xl. note. ii.), whereof accordingly the mind (III. Def. i.), in so far as it is eternal, is the adequate or formal cause of such knowledge. Q.E.D.

In proportion, therefore, as a man is more potent in this kind of knowledge, he will be more completely conscious of himself and of God; in other words, he will be more perfect and blessed, as will appear more clearly in the sequel. But we must here observe that, although we are already certain that the mind is eternal, in so far as it conceives things under the form of eternity, yet, in order that what we wish to show may be more readily explained and better understood, we will consider the mind itself, as though it had just begun to exist and to understand things under the form of eternity, as indeed we have done hitherto; this we may do without any danger of error, so long as we are careful not to draw any conclusion, unless our premisses are plain.