Ética, Parte IV, Proposição 30
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.
Demonstração
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.
Benedict de Spinoza, The Ethics (Ethica Ordine Geometrico Demonstrata), traduzido do latim por R. H. M. Elwes.
Primeira publicação em The Chief Works of Benedict de Spinoza, vol. II (London: George Bell and Sons, 1884).
Esta tradução está em domínio público nos Estados Unidos, onde foi publicada em 1884, e em todos os lugares onde o prazo de direitos autorais é a vida do autor mais 100 anos ou menos; seu tradutor morreu em 1892.
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Texto digital: Project Gutenberg eBook #3800