Be assured that the essential property of piety towards the gods is to form right opinions concerning them, as existing and as governing the universe with goodness and justice. And fix yourself in this resolution, to obey them, and yield to them, and willingly follow them in all events, as produced by the most perfect understanding. For thus you will never find fault with the gods, nor accuse them as neglecting you. And it is not possible for this to be effected any other way than by withdrawing yourself from things not in our own control, and placing good or evil in those only which are. For if you suppose any of the things not in our own control to be either good or evil, when you are disappointed of what you wish, or incur what you would avoid, you must necessarily find fault with and blame the authors. For every animal is naturally formed to fly and abhor things that appear hurtful, and the causes of them; and to pursue and admire those which appear beneficial, and the causes of them. It is impractical, then, that one who supposes himself to be hurt should be happy about the person who, he thinks, hurts him, just as it is impossible to be happy about the hurt itself. Hence, also, a father is reviled by a son, when he does not impart to him the things which he takes to be good; and supposing the empire to be a good made Polynices and Eteocles mutually enemies. On this account the husbandman, the sailor, the merchant, on this account those who lose wives and children, revile the gods. For where interest is, there too is piety placed. So that, whoever is careful to regulate his desires and aversions as he ought, is, by the very same means, careful of piety likewise. But it is also incumbent on everyone to offer libations and sacrifices and first fruits, conformably to the customs of his country, with purity, and not in a slovenly manner, nor negligently, nor sparingly, nor beyond his ability.