It seems to me that each philosophical or religious school has one basic insight that is the foundation and canon for all the rest of its theory and activity. A life lived according to that insight will be most conducive to happiness. For the Epicureans, happiness comes from the satisfaction of simple, natural desires. For the Stoics it comes from going with the natural flow of the cosmos. For the Aristotelians it comes from the fulfillment of one's nature. For the Platonists it comes from union with the God from whom all reality flows. And for the Christians it comes from transformation through union with Jesus.
