Protagoras, the sophist, left it to his pupils to settle the amount of fee that he should receive.

When there is no agreement, we must render what is in our power, for example, to the gods and to our parents (I.).

Cases may arise of conflicting obligation; as, shall we prefer a friend to a deserving man?
shall a person robbed reciprocate to robbers?
and others.

[We have here the germs of Casuistry.] (II.) As to the termination of Friendship; in the case of the useful and the pleasant, the connexion ceases with the motives.

In the case of the good, it may happen that one party counterfeits the good, but is really acting the useful or the pleasant; or one party may turn out wicked, and the only question is, how far hopes of his improvement shall be entertained.
Again, one may continue the same, while the other makes large advances in mental training; how far shall present disparity operate against old associations?
(III.).