I’ll summarize Rand’s foundation for her reason-based morality:
You have only two existential options: existence or non-existence, meaning, in regards to living beings, life or death.
Matter is unconditional, it exists no matter what, without requirement. However life is conditional, it requires maintenance, meaning a specific course of action to maintain its life.
Matter faces no alternatives, it will continue to exist regardless. Only living organisms face the question of life or death.
Life is self-sustaining, requiring self-generated action to further its existence as life. If an organism fails to sustain itself, it dies and only nonliving chemical elements are left.
The concept of ‘life’ is what makes the concept of ‘value’ possible, nothing can be good or evil to a non-living thing which cannot be created or destroyed or fundamentally harmed, only changed into other forms of matter.
So, a plant or animal must feed itself to survive. It needs water, food, shelter, a specific temperature range, etc. These are the values which nature has forced living organisms to pursue. “Its life is the standard of value directing its actions.”
A plant has no choice, its processes are all subconscious. An animal can make choices, but its decisions are guided by instinct with very limited powers of observation and learning. So long as it lives, it acts to further its life by instinct, not by reason, for an animal cannot conceptualize. Because of instinct, it acts always for its own good, unable to choose actions which would destroy itself. And when it meets a situation which instinct cannot deal with, it dies.
“Man has no automatic code of survival. His particular distinction from all other living species is the necessity to act in the face of alternatives by means of volitional choice. He has no automatic knowledge of what is good for him or evil, what values his life depends on, what course of action it requires… Man must obtain his knowledge and choose his actions by a process of thinking, which nature will not force him to perform. Man has the power to act as his own destroyer—and that is the way he has acted through most of his history…”
Man is a rational being, but rationality is a matter of choice. Man has to hold his life as a value as a matter of choice. He has no innate code of instinct to guide his actions, but must think, learn, and reason in order to preserve his life. He has to discover what values sustain his life, and his virtues then consist of the actions that obtain those values.
“A code of values accepted by choice is a code of morality. All that which is proper to the life of a rational being is the good; all that which destroys it is the evil.”
You must think and reason to survive. "Man’s life is the standard of morality, but your own life is its purpose. If existence on earth is your goal, you must choose your actions and values by the standard of that which is proper to man—for the purpose of preserving, fulfilling and enjoying the irreplaceable value which is your life.”
All of that will be familiar for anyone who read through Atlas Shrugged.
A rational standard of morality may quite possibly be the single greatest contribution to philosophy of Rand’s. An objective rational morality means we can finally achieve a -true- separation of church and state, not the pseudo separation we rely on now, where legislation is just the embodiment into law of someone’s religious philosophy. It is a secular morality without appeal to any great book, and thus the most inclusive and fair possible morality.