IV. xxxi.
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.
For that thing is to man most useful, which is most in harmony
with his nature (IV. xxxi. Coroll.); that is, obviously, man.
But man acts absolutely according to the laws of his nature, when
he lives in obedience to reason (III. 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. Def. viii.), the more is he endowed with power to
act according to the laws of his own nature, that is to live in
obedience to reason. But men are most in natural harmony, when
they live in obedience to reason (by the last Prop.); therefore
(by the foregoing Coroll.) men will be most useful one to
another, when each seeks most that which is useful to him.
Q.E.D.

Note.--What we have just shown is attested by experience so
conspicuously, that it is in the mouth of nearly everyone: "Man
is to man a God." Yet it rarely happens that men live in
obedience to reason, for things are so ordered among them, that
they are generally envious and troublesome one to another.
Nevertheless they are scarcely able to lead a solitary life, so
that the definition of man as a social animal has met with
general assent; in fact, men do derive from social life much
more convenience than injury. Let satirists then laugh their
fill at human affairs, let theologians rail, and let misanthropes
praise to their utmost the life of untutored rusticity, let them
heap contempt on men and praises on beasts; when all is said,
they will find that men can provide for their wants much more
easily by mutual help, and that only by uniting their forces can
they escape from the dangers that on every side beset them: not
to say how much more excellent and worthy of our knowledge it is,
to stud