Only insofar as men live in obedience to reason do they necessarily agree in nature; therefore nothing is more useful to man than a rational man, and men are most useful to one another when each seeks what is useful to himself.

By Baruch Spinoza, from Ethics

Key Arguments

  • Men are active only insofar as they act in obedience to reason; what follows from human nature as defined by reason is necessarily good for human nature and in harmony with each individual’s nature.
  • Hence, insofar as they live by reason, men necessarily live in harmony with one another.
  • Corollary I: That which is most in harmony with our nature is most useful; a man lives absolutely according to his nature when he lives by reason and thus is in harmony with other men—therefore no individual thing is more useful to man than a rational man.
  • Corollary II: The more a man seeks what is useful to him, the more he is endowed with virtue (power to act according to his nature), i.e., to live by reason; men are most in natural harmony when living by reason; therefore they are most useful to one another when each seeks what is useful to himself.

Source Quotes

We can easily show in like manner, that all other causes of hatred depend solely on differences, and not on the agreement between men's natures. PROP. XXXV. In so far only as men live in obedience to reason, do they always necessarily agree in nature. Proof.—In so far as men are assailed by emotions that are passions, they can be different in nature (IV. xxxiii.), and at variance one with another.
Coroll.); in other words, such things as are in harmony with each man's nature. Therefore, men in so far as they live in obedience to reason, necessarily live always in harmony one with another. Q.E.D. Corollary I.—There is no individual thing in nature, which is more useful to man, than a man who lives in obedience to reason.
Therefore, men in so far as they live in obedience to reason, necessarily live always in harmony one with another. Q.E.D. Corollary I.—There is no individual thing in nature, which is more useful to man, than a man who lives in obedience to reason. For that thing is to man most useful, which is most in harmony with his nature (IV. xxxi.
Def. ii.), and to this extent only is always necessarily in harmony with the nature of another man (by the last Prop.); wherefore among individual things nothing is more useful to man, than a man who lives in obedience to reason. Q.E.D. Corollary II.—As every man seeks most that which is useful to him, so are men most useful one to another. For the more a man seeks what is useful to him and endeavours to preserve himself, the more is he endowed with virtue (IV. xx.), or, what is the same thing (IV.

Key Concepts

  • PROP. XXXV. In so far only as men live in obedience to reason, do they always necessarily agree in nature.
  • Therefore, men in so far as they live in obedience to reason, necessarily live always in harmony one with another.
  • Corollary I.—There is no individual thing in nature, which is more useful to man, than a man who lives in obedience to reason.
  • Corollary II.—As every man seeks most that which is useful to him, so are men most useful one to another.

Context

Ethics, Part IV, Proposition XXXV with Proof and Corollaries I–II (lines 3265–3395)