ery kind of passion. This state of things
gave rise to the exclamation of the poet:[12]----
"The better path I gaze at and approve,
The worse--I follow."

[12] Ov. Met. vii.20, "Video meliora proboque, Deteriora sequor."

Ecclesiastes seems to have had the same thought in his mind,
when he says, "He who increaseth knowledge increaseth sorrow." I
have not written the above with the object of drawing the
conclusion, that ignorance is more excellent than knowledge, or
that a wise man is on a par with a fool in controlling his
emotions, but because it is necessary to know the power and the
infirmity of our nature, before we can determine what reason can
do in restraining the emotions, and what is beyond her power. I
have said, that in the present part I shall merely treat of human
infirmity. The power of reason over the emotions I have settled
to treat separately.

PROP. XVIII. Desire arising from pleasure is, other conditions
being equal, stronger than desire arising from pain.

Proof.--Desire is the essence of a man (Def. of the Emotions,
i.), that is, the endeavour whereby a man endeavours to persist
in his own being. Wherefore desire arising from pleasure is, by
the fact of pleasure being felt, increased or helped; on the
contrary, desire arising from pain is, by the fact of pain being
felt, diminished or hindered; hence the force of desire arising
from pleasure must be defined by human power together with the
power of an external cause, whereas desire arising from pain must
be defined by human power only. Thus the former is the stronger
of the two. Q.E.D.

Note.--In these few remarks I have explained the causes of
human infirmity and inconstancy, and shown why men do not abide
by the precepts of reason. It now remains for me to show what
course is marked out for us by reason, which of the emotions are
in harmony with the rules of human reason, and which of them are
contrary thereto. But, before I begin to prove my Propositions
in detailed geometrical fashion, it is advisable to sketch them
briefly in advance, so that everyone may more readily grasp my
meaning.

As reason makes no demands contrary to nature, it demands,
that every man should love himself, should seek that which is
useful to him--I mean, that which is really useful to him, should
desire everything which really brings man to greater perfection,
and should, each for himself, endeavour as far as he can to
preserve his own being. This