Some Fundamental Concepts in Ethics
"Ethics" may be broadly defined as that division of philosophy which deals with questions concerning the nature of value in matters of human conduct.
While virtually all people are concerned with making ethical judgments and decisions, philosophers in particular are concerned to
            a) explicate the nature of such judgments in general and
            b) provide criteria for determining what is ethically right or wrong, and
            c) analyze the grounds or reasons we have for holding them to be correct.

Those concerned exclusively with telling us what is right or wrong, good or bad, in matters of human conduct may be termed "moralists." While philosophers have sometimes been moralists, as philosophers their primary concern is not so much to provide moral prescriptions as it is to explain why what we consider to be "right" or "good" is right or good. To do so, philosophers engaged with such questions have generally sought to formulate and justify "ethical theories" which are intended to explain the fundamental nature of that which is "good," why it is "good," and why the ethical principles which are most commonly used to evaluate human conduct follow (or do not follow) from this theory of that which is good.

While there are of course many words in English (as well as most languages) which refer to positive and negative values, we may simplify our vocabulary by taking the words "good" and "bad" to refer to positive and negative values respectively in judgments with respect to people and things, and "right" or "wrong" to refer to positive and negative values respectively with respect to actions. In this way of speaking, then, a "good person" will simply be one whose actions are "right" by the criteria of whatever ethical theory is the basis of such a judgment.

If we restrict attention to actions, any "action" may be analyzed as involving an actor, the person who does the action, and an end result or outcome of the action. In ethical terminology the actor is called the "agent," and the end result is the "consequence" of the action.

Ethical theories may be presented for various purposes. Some theories may merely purport to describe what people do, in fact (so it is claimed), consider to be "good" or "right." Such theories are "descriptive ethical theories" and may be considered "true" or "false" depending on whether or not they do indeed describe correctly what people in fact do consider good or right. Since such descriptive theories are concerned with what people actually do believe and what motivates them to believe what they do, such theories are strictly speaking more the concern of psychology than philosophy, and their acceptability is a matter of whether or not the empirical evidence indicates that what they say about human values is in fact the case. Since they are restricted to telling us what is the case, descriptive ethical theories cannot serve as the basis for making claims intended to change or persuade people to act or think otherwise than the way they do.

In contrast to descriptive ethical theories, those ethical theories which are intended to justify judgments concerning what people ought or should do (or not do), are called "normative ethical theories." Normative theories characteristically yield ethical judgments which have in them the key concept of "ought" or "should" (or some such synonym). Their concern is not with what is the case, but with what should be the case; they are concerned not with the "real" (what is so), but with the "ideal" (what ought to be). As such, unlike a purely descriptive theory, a normative theory cannot be "refuted" by appeal to the facts of human behavior, for the defender of a normative claim can always reply, yes, it is true people do not in fact behave this way, but they ought to. Normative theories are not the concern of psychologists, but of philosophers and (typically) moralists. The person who seeks to change, to improve or reform, human behavior must defend a normative theory, and it is this kind of theory which most people have in mind in examining what philosophers have to say about ethics.

Ethical theories can be divided into two categories depending on what they consider the source of ethical value to be: consequentialist or "teleological" ethical theories and motivational or "deontological" ethical theories.

A consequentialist or "teleological ethical theory" claims that what makes an action right or wrong are the consequences of the action; quite simply a "right action" is one which has good consequences, a "wrong action" has bad consequences. (Of course the consequentialist theory still has to specify what makes the consequences good or bad, concerning which, see the next paragraph.)

A "deontological ethical theory" holds in opposition to a consequentialist theory that it is not the consequences but the motivation which prompts the agent to do an action which makes an action right or wrong. On this type of ethical theory an action motivated by the right sorts of reasons will be "right" no matter whether its consequences are desirable or not, whereas an action motivated by the wrong sorts of reasons will be a wrong action, even if its consequences might be considered desirable.

At least in Western philosophy, consequentialist theories have generally also been eudaemonistic ethical theories.
A eudaemonistic consequentialist ethical theory holds that what makes a consequence "good," and hence an action "right," is its tendency to promote human happiness or well-being.
One must make a distinction between the doctrine called "psychological eudaemonism" which holds the descriptive claim that human beings are in fact always motivated by a desire to achieve happiness, and the doctrine called "ethical eudaemonism," which makes the normative claim that people ought always to act so as to achieve happiness. Psychological eudaemonism as a theory about human motivation may be correct or incorrect depending on the empirical evidence psychologists are able to present regarding this view of human motivation. (For most of history, it was common to regard the evidence as favoring such a view, but more recently psychological research tends to call this into question.) Ethical eudaemonism, however, makes a normative claim about what ought to motivate people, and thus cannot be refuted by empirical evidence regarding what does in fact motivate them.
While eudaemonistic theories in general leave open the question of what constitutes human happiness or well-being, the special kind of eudaemonistic theories which define "happiness" as maximum pleasure and minimum pain are called "hedonistic" ethical theories.
Many Western eudaemonistic, consequentialist theories have also been hedonistic theories, most notably epicureanism and utilitarianism. Hedonistic theories may be further subdivided into two groups depending on whose pleasures and pains give an action its ethical value.
"Egoistic hedonism" holds that what makes an action right or wrong is its tendency to maximize pleasures and minimize pains of the agent, the person doing the action.

"Altruistic hedonism" holds that what gives an action its ethical value is its tendency to maximize pleasures and minimize pains of all affected by the action.

Epicureanism is an example of egoistic hedonism, while utilitarianism is an example of altruistic hedonism.

Since what does produce pleasure and pains cannot be deduced from reasoning but can only be known by experience, hedonists are ethical empiricists, who hold that it is only by experience that we can determine the ethical value of an action.

Deontological ethical theories generally have held that what makes an action right is whether the agent is motivated by a desire to follow an "ethical principle." An agent who is so motivated is said to act "out of a sense of duty" or "moral obligation."

Deontological ethical theories are often associated with various revealed religious traditions in that the "ethical principles" which are regarded as determining human moral obligation are in effect claimed to be commands of a divine being. Such theories may be called "theological deontological ethical theories." In philosophy, however, justification of ethical principles cannot proceed by appeal to a religious revelation, but must be made by appeal to rational arguments. There is no need for theological and philosophical deontological theories to conflict; a philosopher might, for example, argue that the ethical principles which reason dictates are the same as those a supreme being has commanded.

Typically philosophers seeking to defend deontological theories have been "rationalists" in the sense that the ethical principles they hold determine human ethical duties are claimed to be deduced by reason from the essential nature of the universe (as in stoicism) or from the nature of human beings as essentially "rational beings" (as in Kantian ethical theory).