PROP. XXVIII. The mind's highest good is the knowledge of God, and the mind's highest virtue is to know God.
Proof.--The mind is not capable of understanding anything higher than God, that is (I. Def. vi.), than a Being absolutely infinite, and without which (I. xv.) nothing can either be or be conceived; therefore (IV. xxvi. and xxvii.), the mind's highest utility or (IV. Def. i.) good is the knowledge of God. Again, the mind is active, only in so far as it understands, and only to the same extent can it be said absolutely to act virtuously. The mind's absolute virtue is therefore to understand. Now, as we have already shown, the highest that the mind can understand is God; therefore the highest virtue of the mind is to understand or to know God. Q.E.D.
PROP. XXIX. No individual thing, which is entirely different from our own nature, can help or check our power of activity, and absolutely nothing can do us good or harm, unless it has something in common with our nature.
Proof.--The power of every individual thing, and consequently the power of man, whereby he exists and operates, can only be determined by an individual thing (I. xxviii.), whose nature (II. vi.) must be understood through the same nature as that, through which human nature is conceived. Therefore our power of activity, however it be conceived, can be determined and consequently helped or hindered by the power of any other individual thing, which has something in common with us, but not by the power of anything, of which the nature is entirely different from our own; and since we call good or evil that which is the cause of pleasure or pain (IV. viii.), that is (III. xi. note), which increases or diminishes, helps or hinders, our power of activity; therefore, that which is entirely different from our nature can neither be to us good nor bad. Q.E.D.
PROP. XXX. A thing cannot be bad for us through the quality which it has in common with our nature, but it is bad for us in so far as it is contrary to our nature.
Proof.--We call a thing bad when it is the cause of pain (IV. viii.), that is (by the Def., which see in III. xi. note), when it diminishes or checks our power of action. Therefore, if anything were bad for us through that quality which it has in common with our nature, it would be able itself to diminish or check that which it has in common with our nature, which (III. iv.) is absurd. Wherefore nothing can be bad for us through that quality which it has in common with us, but, on the other hand, in so far as it is bad for us, that is (as we have just shown), in so far as it can diminish or check our power of action, it is contrary to our nature. Q.E.D.