A Treatise of Human Nature - Volume 3

divided into speculative and practical; and as morality is always included 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 deterred from some actions by the opinion of injustice, and impelled to others by that of obligation.

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 powerless in this particular. The rules of morality, therefore, are not conclusions of our reason.

No one, I believe, will deny the fairness of this inference; nor is there any other way 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 actions, it is in vain to claim that morality is discovered only by a deduction of reason. An active principle