" THE STOICS COULD HAVE given us a philosophy of life without explaining why it is a good philosophy. They could, in other words, have left adoption of their philosophy of life as a leap of faith, the way Zen Buddhists do with theirs. But being philosophers, they felt the need to prove that theirs was the “correct” philosophy of life and that rival philosophies were somehow mistaken. "

― William B. Irvine , A Guide to the Good Life: The Ancient Art of Stoic Joy