i.), which tends to the preservation of our nature, that is (by the hypothesis), which tends to the preservation of the thing itself; but this (III.

vi.) is absurd; therefore, in so far as a thing is in harmony with our nature, it is necessarily good.

Q.E.D.
Corollary .-- Hence it follows, that, in proportion as a thing is in harmony with our nature, so is it more useful or better for us, and vice versa, in proportion as a thing is more useful for us, so is it more in harmony with our nature.

For, in so far as it is not in harmony with our nature, it will necessarily be different therefrom or contrary thereto.

If different, it can neither be good nor bad (IV.