The chief spring or actuating principle of the human mind is pleasure or pain; and when these sensations are removed, both from our thought and feeling, we are, in a great measure, incapable of passion or action, of desire or volition.  The most immediate effects of pleasure and pain are the propense and averse motions of the mind; which are diversified into volition, into desire and aversion, grief and joy, hope and fear, according as the pleasure or pain changes its situation, and becomes probable or improbable, certain or uncertain, or is considered as out of our power for the present moment.  But when along with this, the objects, that cause pleasure or pain, acquire a relation to ourselves or others; they still continue to excite desire and aversion, grief and joy:  But cause, at the same time, the indirect passions of pride or humility, love or hatred, which in this case have a double relation of impressions and ideas to the pain or pleasure.

We have already observed, that moral distinctions depend entirely on certain peculiar sentiments of pain and pleasure, and that whatever mental quality in ourselves or others gives us a satisfaction, by the survey or reflection, is of course virtuous; as every thing of this nature, that gives uneasiness, is vicious.  Now since every quality in ourselves or others, which gives pleasure, always causes pride or love; as every one, that produces uneasiness, excites humility or hatred:  It follows, that these two particulars are to be considered as equivalent, with regard to our mental qualities, virtue and the power of producing love or pride, vice and the power of producing humility or hatred.  In every case, therefore, we must judge of the one by the other; and may pronounce any quality of the mind virtuous, which causes love or pride; and any one vicious, which causes hatred or humility.

If any action be either virtuous or vicious, it is only as a sign of some quality or character.  It must depend upon durable principles of the mind, which extend over the whole conduct, and enter into the personal character.  Actions themselves, not proceeding from any constant principle, have no influence on love or hatred, pride or humility; and consequently are never considered in morality.

This reflection is self-evident, and deserves to be attended to, as being of the utmost importance in the present subject.  We are never to consider any single action in our enquiries concerning the origin of morals; but only the quality or character from which the action proceeded.  These alone are durable enough to affect our sentiments concerning the person.  Actions are, indeed, better indications of a character than words, or even wishes and sentiments; but it is only so far as they are such indications, that they are attended with love or hatred, praise or blame.

To discover the true origin of morals, and of that love or hatred, which arises from mental qualities, we must take the matter pretty deep, and compare some principles, which have been already examined and explained.