of
this subject as a branch of the philosophy of the intellectual powers, I
endeavoured to shew the grounds on which we believe, that there are
facts, truths, motives, or moral causes, which have a tendency thus to
influence the determinations of the mind, with a uniformity similar to
that which we observe in the operation of physical causes. For the due
operation of moral causes, indeed, certain circumstances are required in
the individual on whom they are expected to operate, and, without these,
they may fail in their operation. It is necessary that he should be
fully informed in regard to them as truths addressed to his
understanding,--that he direct his attention to them with suitable
intensity, and exercise his reasoning powers upon their tendencies,--and
that he be himself in a certain healthy state of moral feeling. In all
our intercourse with mankind, accordingly, we proceed upon an absolute
confidence in the uniformity of the operation of these causes, provided
we are acquainted with the moral condition of the individual. We can
foretel, for example, the respective effects which a tale of distress
will have upon a cold-hearted miser, and a man of active benevolence,
with the same confidence with which we can predict the different actions
of an acid upon an alkali and upon a metal;--and there are individuals
in regard to whose integrity and veracity, in any situation in which
they can be placed, we have a confidence similar to that with which we
rely on the course of nature. In this manner we gradually acquire, by
experience, a knowledge of mankind; precisely as, by observation or
experiment, we acquire a knowledge of the operation of physical agents.
Thus we come to know that one man is absolutely to be relied on, in
regard to a particular line of conduct in given circumstances;--and that
another is not to be relied on, if any thing should come in the way,
affecting his own pleasure or interest. In endeavouring to excite
various individuals to the same conduct in a particular case, we learn,
that in one, we have to appeal only to his sense of duty,--in another,
to his love of approbation;--while, on a third, nothing will make any
impression except what bears upon his interest or his pleasure. Again,
when we find that, in a particular individual, certain motives or truths
fail of the effects which we have observed them to produce in others, we
endeavour to impress them upon his mind, and to rouse his attention to