When, therefore, any one identifies his interest with those of sanctity, virtue, country, parents, and friends, all these are secured; but whenever he places his interest in anything else than friends, country, family and justice, then these all give way, borne down by the weight of self-interest. For wherever I and mine are placed, thither must every living being gravitate. If in body, that will sway us; if in our own will, that; if in externals, these. If, therefore, I rest my personality in the will, then only shall I be a friend, a son, or a father, such as I ought. For in that case it will be for my interest to preserve the faithful, the modest, the patient, the abstinent, the beneficent character; to keep the relations of life inviolate. But if I place my personality in one thing, and virtue in another, the doctrine of Epicurus will stand its ground, that virtue is nothing, or mere opinion.

Epiktet