They never mistake a present pleasure or pain; they always act correctly upon that.

They are the victims of deceitful appearances; they make wrong judgments in comparing present with future pains, such is the weakness of the mind's constitution in this department.

Our wrong judgments proceed partly from ignorance and partly from inadvertence, and our preference of vice to virtue is accounted for by these wrong judgments.
Chap.XXVIII.discusses Moral Relations.

Good and Evil are nothing but Pleasure and Pain, and what causes them.

Moral Good or Evil is the conformity or unconformity of our voluntary actions to some Law, entailing upon us good or evil by the will and power of the Law-giver, to which good and evil we apply the names Reward and Punishment.
There are three sorts of Moral Rules: 1st, The Divine Law, whether promulgated by the Light of Nature or by Revelation, and enforced by rewards and punishments in a future life.