Philosophy was defined by the Stoics as 'the knowledge of things divine and human'.

When Socrates declared before his judges that "there is no evil to a good man either in life or after death, nor are his affairs neglected by the gods", he sounded the keynote of Stoicism, with its two main doctrines of virtue as the only good, and the government of the world by Providence. Let us weigh his words, lest we interpret them by the light of a comfortable modern piety. A great many things that are commonly called evil may and do happen to a good man in this life, and therefore presumably misfortunes may also overtake him in any other life that there may be. The only evil that can never befall him is vice, because that would be a contradiction in terms. Unless therefore Socrates was uttering idle words on the most solemn occasion of his life, he must be taken to have meant that there is no evil but vice, which implies that there is no good but virtue. Thus we are landed at once in the heart of the Stoic morality. To the question why, if there be a providence, so many evils happen to good men, Seneca unflinchingly replies: "No evil can happen to a good man, contraries do not mix." God has removed from the good all evil: because he has taken from them crimes and sins, bad thoughts and selfish designs and blind lust and grasping avarice. He has attended well to themselves, but he cannot be expected to look after their luggage: they relieve him of that care by being indifferent about it. This is the only form in which the doctrine of divine providence can be held consistently with the facts of life Again, when Socrates on the same occasion expressed his belief that it was not "permitted by the divine law for a better man to be harmed by a worse", he was asserting by implication the Stoic position...