Ethics is a branch of philosophy which studies the nature and logic of what is good and morally right. Ethics is typically broken into at least five different subjects, including meta-ethics, the value theory, the theory of conduct, and applied ethics. Each of these will be introduced below.
First, we need to define an "ethical sentence", also called a normative statement. An ethical sentence contains the words "good," "bad," "right," "wrong," "moral," "immoral," or any other word that describes a value. In other words, these are words that we use to morally evaluate people, intentions, actions, and other sorts of things.
For example: "Sally is a good person"; "it is wrong to steal"; "it is totally evil to do what they are contemplating"; "the senator’s actions were thoroughly unethical." And correspondingly a non-ethical sentence would be a sentence that does not contain one of these terms of moral evaluation. Examples would include: "That flower is red"; "Norman is six foot three"; "Juneau is the capital of Alaska"; and so forth.
So now let’s look at those different areas of ethics mentioned above.
Meta-ethics is the study of what sort of meaning ethical sentences have. What exactly do we mean when we say "murder is wrong"?
The second area, the theory of value, asks: "What sorts of things, and situations, are good?" Notice, the goodness we are talking about here is the goodness, or desirability, or the value, of things -- not of people or actions. The goodness of people and their actions is studied under the next heading, theory of conduct.
Obviously, there is a difference between calling a banana split "good" and calling a human being "good." The theory of value is more concerned about the sense in which objects like banana splits, or situations like a well-paying job, or mental states like pleasure, are good.
However, it might be right to include the sense of "human goodness" in the sense of which objects and mental states and situations can be good. Maybe ultimately it is possible to define what it means to be a good person in terms of that person’s tendency to create good things and situations for himself and other people. Perhaps calling someone "a good person" is, in some sense, "a person who creates a lot of good for the world." Such possibilities are examined in the theory of conduct.
A theory of conduct studies what is right, obligated, permitted, required by duty, and what is more than duty requires. It also studies the opposites of these things: what is wrong, forbidden, denied, and evil. Theories of conduct try to answer questions like: "How should I act, and why?" So theories of conduct debate the ultimate standards of right and wrong -- standards of morality, or moral rules. For example, a familiar moral rule is the "Golden Rule": "Do unto others as you would have them do unto you."
Another area is applied ethics. It applies ethical theories to particular ethical problems. Most academic ethical problems are about public policy. Such as: Is getting an abortion ever moral? Is euthanasia ever moral? What are the ethical underpinnings of affirmative action policies? What is the basis (if any) of animal rights? And so forth.
But not all questions studied in applied ethics concern public policy. For example: What is lying and is lying always wrong? If not, when is lying permissible?
Casuistry is an approach to applied ethics.
The above is based on a portion of Larrys Text, wikification is invited. In fact, if you can do better, you can feel free to replace this--please, just don't reduce the amount of useful content. See Larrys Text for further notes and comments.