If the thought and understanding were alone capable of fixing the boundaries of right and wrong, the character of virtuous and vicious either must lie in some relations of objects, or must be a matter of fact which is discovered by our reasoning. This consequence is evident. As' the operations of human understanding divide themselves into two kinds, the comparing of ideas, and the inferring of matter of fact, were virtue discovered by the understanding, it must be an object of one of these operations; nor is there any third operation of the understanding which can discover it. There has been an opinion very industriously propagated by certain philosophers, that morality is susceptible of demonstration; and though no one has ever been able to advance a single step in those demonstrations, yet tis 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 'tis allowed on all hands, that no matter of fact is capable of being demonstrated. Let us therefore begin with examining this hypothesis, and endeavour, if possible, to fix those moral qualities which have been so long the objects of our fruitless researches; point out distinctly the relations which constitute morality or obligation, that we may know wherein they consist, and after what manner we must judge of them. If you assert that vice and virtue consist in relations susceptible of 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 to lie in the relations, and as there is no one of these relations but what is applicable, not only to an irrational but also to an inanimate object, it follows, that even such objects must be susceptible of merit or demerit. _Resemblance, contrariety, degrees in quality_, and _proportions in quantity and number_; all these relations belong as properly to matter, as to our actions, passions, and volitions. 'Tis unquestionable, therefore, that morality lies not in any of these relations, nor the sense of it in their discovery.[3] Should it be asserted, that the sense of morality consists in the discovery of some relation distinct from these, and that our enumeration was not complete when we comprehended all demonstrable relations under four general heads; to this I know not what to reply, till some one be so good as to point out to me this new relation. 'Tis impossible to refute a system which has never yet been explained. In such a manner of fighting in the dark, a man loses his blows in the air, and often places them where the enemy is not present.