The Natural Law as developed by Aristotle, Maimonides, Thomas Aquinas & a whole host of others....the canon of Judeo-Christian civilization & its consequences for the way (some) people think. You don't need to have read a word of any of them, or be a believer, for the good stuff to have sunk into your consciousness.

Kinda like mother's milk for the mind. Those who reject it all run the risk of becoming monstrous arseholes.