He then discusses the question, (on which he had charged Hume with mistake), ‘Why is approbation confined to voluntary acts?’ He thinks it but a partial solution to say that approbation and disapprobation are wasted on what is not in the power of the will.  The full solution he considers to be found in the mode of derivation of the moral sentiment; which, accordingly, he re-discusses at some length.  He produces the analogies of chemistry to show that compounds may be totally different from their elements.  He insists on the fact that a derived pleasure is not the less a pleasure; it may even survive the primary pleasure.  Self-love (improperly so called) is intelligible if its origin be referred to Association, but not if it be considered as prior to the appetites and passions that furnish its materials.  And as the pleasure derived from low objects may be transferred to the most pure, so Disinterestedness may originate with self, and yet become as entirely detached from that origin as if the two had never been connected.

He then repeats his doctrine, that these social or disinterested sentiments prompt the will as the means of their gratification.  Hence, by a farther transfer of association, the voluntary acts share in the delight felt in the affections that determine them.  We then desire to experience beneficent volitions, and to cultivate the dispositions to these.  Such dispositions are at last desired for their own sake; and, when so desired, constitute the Moral Sense, Conscience, or the Moral Sentiment, in its consummated form.  Thus, by a fourth or fifth stage of derivation from the original pleasures and pains of our constitution, we arrive at this highly complex product, called our moral nature.

Nor is this all.  We must not look at the side of indignation to the wrong-doer.  We are angry at those who disappoint our wish for the happiness of others; we make their resentment our own.  We hence approve of the actions and dispositions for punishing such offenders; while we so far sympathize with the culprit as to disapprove of excess of punishment.  Such moderated anger is the sense of Justice, and is a new element of Conscience.  Of all the virtues, this is the one most directly aided by a conviction of general interest or utility.  All laws profess it as their end.  Hence the importance of good criminal laws to the moral education of mankind.

Among contributary streams to the moral faculty, he enumerates courage, energy, and decision, properly directed.

He recognizes ‘duties to ourselves,’ although condemning the expression as absurd.  Intemperance, improvidence, timidity are morally wrong.  Still, as in other cases, a man is not truly virtuous on such points, till he loves them for their own sake, and even performs them without an effort.  These prudential qualities having an influence on the will, resemble in that the other constituents of Conscience.  As a final result, all those sentiments whose object is a state of the will become intimately and inseparably blended in the unity of Conscience, the arbiter and judge of human actions, the lawful authority over every motive to conduct.