For all living beings, life is an ongoing process that requires continuous action to gain and keep the values necessary for their survival. Whether they do it by complex biochemical processes, such as plants and simple organisms, by hunting down they prey, such as the higher animals, or by living in a modern industrial society, such as human beings, all living beings must daily affirm their nature, instinct, or desire to remain living.
Like all living beings, man requires certain values to survive, but he is unique in that he can and must choose the values necessary for his life because he has no automatic means of doing so. His ability to reason, or to experience the world around him and comprehend it by the use of logic gives man the capacity to both understand the values his life requires and the knowledge of how to achieve them. Faced with the basic moral alternative of acting to remain alive or drifting towards death, man must use reason to choose the values necessary for his life, and then achieve them. From the earliest hunter and gatherer, whose work consistent almost entirely of manual labor to a computer programmer (or a philosopher) whose work is almost entirely intellectual, each man must exercise his mind to create the values necessary to sustain his life.
“There is only one fundamental alternative in the universe: existence or non-existence—and it pertains to a single class of entities: to living organisms. The existence of inanimate matter is unconditional, the existence of life is not: it depends on a specific course of action. Matter is indestructible, it changes its forms, but it cannot cease to exist. 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, For the New Intellectual, p121)
"Only a living entity can have goals or can originate them. And it is only a living organism that has the capacity for self-generated, goal-directed action. On the physical level, the functions of all living organisms, from the simplest to the most complex—from the nutritive function in the single cell of an amoeba to the blood circulation in the body of a man—are actions generated by the organism itself and directed to a single goal: the maintenance of the organism's life.""The Objectivist Ethics", The Virtue of Selfishness, p16