He then discusses the bearing of ignorance and error, vincible and invincible, and specially the case wherein an erroneous conscience extenuates.

The difficulty of such cases, he says, are due to ambiguity, wherefore he distinguishes three meanings of Conscience that are found, (1) the moral faculty, (2) the judgment of the understanding about the springs and effects of actions, upon which the moral sense approves or condemns them, (3) our judgments concerning actions compared with the _law_ (moral maxims, divine laws, &c.).
In Chapter II., he lays down general rules of judging about the morality of actions from the affections exciting to them or opposing them; and first as to the degree of virtue or vice when the ability varies; in other words, morality as dependent on the _strength_ of the affections.

Next, and at greater length, morality as dependent on the _kind_ of the affections.
Here he attempts to fix, in the first place, the degree of benevolence, as opposed to private interest, that is necessary to render men virtuous, or even innocent, in accordance with his principle that there is implanted in us a very high standard of necessary goodness, requiring us to do a public benefit, when clear, however burdensome or hurtful the act may be to ourselves; in the second place, the proportion that should be kept between the narrower and the more extensive generous affections, where he does not forget to allow that, in general, a great part of human virtue must necessarily lie within the narrow range.

Then he gives a number of special rules for appreciating conduct, advising, _for the very sake of the good to others that will result therefrom_, that men should foster their benevolence by the thought of the advantage accruing to themselves here and hereafter from their virtuous actions; and closes with the consideration of the cases wherein actions can be imputed to other than the agents.
In Chapter III., he enters into the general notion of Rights and Laws, and their divisions.

From _right_ use of such affection or actions as are approved by the moral faculty from their relation to the general good, or the good of particular persons consistently with the general good, he distinguishes the _right_ of a man to do, possess, demand, &c., which exists when his doing, possessing, &c.