Ethics, or morality, is a code of values to guide man’s actions and decisions. The actions and decisions that a man makes determine the purpose and direction of his life. A value is “that which one acts to gain and/or keep.” Water and sunshine are valuable to plants, money, health and friendship are valuable to man. Organisms must do something, either intentionally or not, to achieve certain ends. Ethics is concerned with what one should seek and how one should act. Nonliving things have nothing at stake. Nothing is good or bad for a river, a rock or a tree. What happens to those things might matter for some organism (such as a river flooding a city to it’s residents, the tree to an owl for it’s nest) but not for these objects intrinsically.
Living things have something at stake -- their life. This alternative, life or death, is at the bottom of every alternative faced by a living organism. It is fundamental and inescapable. Every action, however indirectly, either helps or hurts a organism to survive. An organisms continued existence is not assured -- certain actions must be taken by it to survive. Organisms must achieve the values it’s nature requires.
As with any organism, the kinds of actions human beings take either impede or advance their life. These are facts of reality that we can observe and apply reason to. In other words, they are objective. They also apply to all human beings, since we all face the same choice and have the same essential nature. This is why ethical principles (a principle being a “general truth on which other truths depend” can be applied by all men to all areas of their lives where alternatives are available to him.
Since the struggle to survive is what causes values to be possible and requires the achievement of values, life is the unit-of-measure to determine what is good or bad for a man. The proper standard of ethics is man’s life