Stockdale on Stoicism 23

What are some of the guidelines to identifying the good and the evil in Stoic thought?

Well, first, Stoicism goes back to the idea that Nature is God's body, and that it doesn't do to try to improve on it. 

In fact, God and Nature are two aspects of the same thing. God's Soul is the Mind of the Universe, and Nature is his body. Just as the Mind is the active, and Nature is the passive, so our minds are active and our bodies passive. Mind over matter; it all happens in your head, so don't worry about your body. 

The perfect man models himself on this operation of the Universe. Nothing is ever lost. All remains in the care of Providence. Just as the Universe, in which the Mind of God is imminent and indwelling and moves in a manner self-sufficient and self-ruling, so the good man is independent, autonomous, a law unto himself and a follower of the eternal guidance of duty and conscience.

This is called the coherence of Stoicism, and Cicero used this as the basis of his founding of Natural Law and International Law. "True law is right reason in agreement with Nature." 

—from James B. Stockdale, The Stoic Warrior's Triad