rightly observing the two former cautions; the appearance there is
of some small diversity amongst mankind with respect to this
faculty, with respect to their natural sense of moral good and evil;
and the attention necessary to survey with any exactness what passes
within, have occasioned that it is not so much agreed what is the
standard of the internal nature of man as of his external form.
Neither is this last exactly settled. Yet we understand one another
when we speak of the shape of a human body: so likewise we do when
we speak of the heart and inward principles, how far soever the
standard is from being exact or precisely fixed. There is therefore
ground for an attempt of showing men to themselves, of showing them
what course of life and behaviour their real nature points out and
would lead them to. Now obligations of virtue shown, and motives to
the practice of it enforced, from a review of the nature of man, are
to be considered as an appeal to each particular person's heart and
natural conscience: as the external senses are appealed to for the
proof of things cognisable by them. Since, then, our inward
feelings, and the perceptions we receive from our external senses,
are equally real, to argue from the former to life and conduct is as
little liable to exception as to argue from the latter to absolute
speculative truth. A man can as little doubt whether his eyes were
given him to see with as he can doubt of the truth of the science of
optics, deduced from ocular experiments. And allowing the inward
feeling, shame, a man can as little doubt whether it was given him
to prevent his doing shameful actions as he can doubt whether his
eyes were given him to guide his steps. And as to these inward
feelings themselves, that they are real, that man has in his nature
passions and affections, can no more be questioned than that he has
external senses. Neither can the former be wholly mistaken, though
to a certain degree liable to greater mistakes than the latter.