E4P31D
Demonstration — Part IV
Latin
Quatenus enim res aliqua cum nostra natura convenit, non potest (per propositionem præcedentem) esse mala. Erit ergo necessario vel bona vel indifferens. Si hoc ponatur nempe quod neque bona sit neque mala, nihil ergo (per definitionem 1 hujus) ex ipsius natura sequetur quod nostræ naturæ conservationi inservit hoc est (per hypothesin) quod ipsius rei naturæ conservationi inservit sed hoc est absurdum (per propositionem 6 partis III); erit ergo quatenus cum nostra natura convenit, necessario bona. Q.E.D.
English (Elwes 1883)
In so far as a thing is in harmony with our nature, it cannot be bad for it. It will therefore necessarily be either good or indifferent. If it be assumed that it be neither good nor bad, nothing will follow from its nature (IV. Def. 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.
Modern English
In so far as a thing agrees with our nature, it cannot be bad for us (E4P30). It must therefore be either good or indifferent. Suppose it is neither good nor bad: then nothing would follow from its nature that serves to preserve our nature (E4D1), that is, (by the hypothesis), nothing that serves to preserve its own nature. But this (E3P6) is absurd. Therefore, in so far as a thing agrees with our nature, it is necessarily good.