《伦理学》，第IV部分，命题27
We know nothing to be certainly good or evil, save such things as really conduce to understanding, or such as are able to hinder us from understanding.
证明
The mind, in so far as it reasons, desires nothing beyond understanding, and judges nothing to be useful to itself, save such things as conduce to understanding (by the foregoing Prop.). But the mind (II. xli., xliii. and note) cannot possess certainty concerning anything, except in so far as it has adequate ideas, or (what by II. xl. note, is the same thing) in so far as it reasons. Therefore we know nothing to be good or evil save such things as really conduce, &c. Q.E.D.
Benedict de Spinoza, The Ethics (Ethica Ordine Geometrico Demonstrata), 由R. H. M. Elwes译自拉丁文.
首次出版于The Chief Works of Benedict de Spinoza，第II卷（London：George Bell and Sons，1884）。
本译文在美国已超出版权保护期（1884年出版于美国），在版权期限为作者终身加100年或更短的任何地方同样如此；其译者卒于1892年。
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