“It is only a living organism that faces a constant alternative: the issue of life or death. Life is a process of self-sustaining and self-generated action. If an organism fails in that action, it dies; its chemical elements remain, but its life goes out of existence. It is only the concept of ‘Life’ that makes the concept of ‘Value’ possible. It is only to a living entity that things can be good or evil.” — Ayn Rand
The good is that which sustains one’s life. The evil is that which destroys one’s life. The standard that determines whether an action is for good or evil is one’s life.
 Ayn Rand “The Objectivist Ethics” The Virtue of Selfishness 15