“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.
 Ayn Rand “The Objectivist Ethics” The Virtue of Selfishness 15