"Master, there must be an absolute fundament of ethics. Is there such a thing?"
"Naturally there is. Perhaps though, you may be rather young for understanding. Yet, of the whole set of rules, the fourth definition is the clearest. It is found in practically all ancients, it crops up in almost all our daily conversations (Conf.112, [135], Tao Te 59, Seneca Lett.47.14.). When you say: 'imagine that...' or 'suppose that ...', you use the other.
The measure for our behaviour is that what you would like in others. Was it not Cicero who said that in order to know in a fair way what to do with one who had murdered his father, ask him what he would do with his son should he ... ?"
"But master, that would be revenge!"
"Excellent young man, but remember it was in the days of legal (?) slavery and other bestialities, some 2000 years ago. Young as you well may be, just try and think of the three preceding rules yourself, then, tell me. They are just as clear and just as fundamental." [49], [61], [76], [136]