A Treatise of Human Nature
Those who affirm that virtue is nothing but a conformity to reason; that there are eternal
fitnesses and unfitnesses of things, which are the same to every rational being that
considers them; that the immutable measures of right and wrong impose an obligation,
not only on human creatures, but also on the Deity himself: All these systems concur in
the opinion, that morality, like truth, is discerned merely by ideas, and by their juxta-
position and comparison. In order, therefore, to judge of these systems, we need only
consider, whether it be possible, from reason alone, to distinguish betwixt moral good
and evil, or whether there must concur some other principles to enable us to make that
If morality had naturally no influence on human passions and actions, it were in vain to
take such pains to inculcate it; and nothing would be more fruitless than that multitude of
rules and precepts, with which all moralists abound. Philosophy is commonly divided
into speculative and practical; and as morality is always comprehended under the latter
division, it is supposed to influence our passions and actions, and to go beyond the calm
and indolent judgments of the understanding. And this is confirmed by common
experience, which informs us, that men are often governed by their duties, and are
detered from some actions by the opinion of injustice, and impelled to others by that of
Since morals, therefore, have an influence on the actions and affections, it follows, that
they cannot be derived from reason; and that because reason alone, as we have already
proved, can never have any such influence. Morals excite passions, and produce or
prevent actions. Reason of itself is utterly impotent in this particular. The rules of
morality. therefore, are not conclusions of our reason.
No one, I believe, will deny the justness of this inference; nor is there any other means of
evading it, than by denying that principle, on which it is founded. As long as it is
allowed, that reason has no influence on our passions and action, it is in vain to pretend,
that morality is discovered only by a deduction of reason. An active principle can never
be founded on an inactive; and if reason be inactive in itself, it must remain so in all its
shapes and appearances, whether it exerts itself in natural or moral subjects, whether it
considers the powers of external bodies, or the actions of rational beings.
It would be tedious to repeat all the arguments, by which I have proved [Book II. Part III.
Sect 3.], that reason is perfectly inert, and can never either prevent or produce any action
or affection. it will be easy to recollect what has been said upon that subject. I shall only
recall on this occasion one of these arguments, which I shall endeavour to render still
more conclusive, and more applicable to the present subject.
Reason is the discovery of truth or falshood. Truth or falshood consists in an agreement
or disagreement either to the real relations of ideas, or to real existence and matter of fact.
Whatever, therefore, is not susceptible of this agreement or disagreement, is incapable of
being true or false, and can never be an object of our reason. Now it is evident our
passions, volitions, and actions, are not susceptible of any such agreement or
disagreement; being original facts and realities, compleat in themselves, and implying no