The Descent of Man

to the feelings caused by other powerful instincts
or desires, when left unsatisfied or baulked.
We compare the weakened impression of a
past temptation with the ever present social
instincts, or with habits, gained in early youth
and strengthened during our whole lives, until
they have become almost as strong as instincts.
If with the temptation still before us we do not
yield, it is because either the social instinct or
some custom is at the moment predominant, or
because we have learnt that it will appear to us
hereafter the stronger, when compared with the
weakened impression of the temptation, and
we realise that its violation would cause us suffering.
Looking to future generations, there is
no cause to fear that the social instincts will
grow weaker, and we may expect that virtuous
habits will grow stronger, becoming perhaps
fixed by inheritance. In this case the struggle
between our higher and lower impulses will be
less severe, and virtue will be triumphant.