A Treatise of Human Nature - Volume 3

SECTION I. Moral distinctions not derived from reason.

ever been able to advance a single step in those demonstrations; yet it is taken for granted that this science may be brought to an equal certainty with geometry or algebra. Upon this supposition, vice and virtue must consist in some relations; since it is allowed on all hands that no matter of fact is capable of being demonstrated. Let us, therefore, begin by examining this hypothesis, and endeavor, if possible, to fix those moral qualities which have been so long the objects of our fruitless research. Point out distinctly the relations which constitute morality or obligation, so that we may know what they consist of and in what manner we must judge them.

If you assert that vice and virtue consist in relations susceptible to certainty and demonstration, you must confine yourself to those four relations which alone admit of that degree of evidence; and in that case, you run into absurdities from which you will never be able to extricate yourself. For as you make the very essence of morality lie in the relations, and as there is no one of these relations that is not applicable not only to an irrational being but also to an inanimate object, it follows that even such objects must be susceptible to merit or demerit.