Introduction to ethics
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The field of ethics deals with what is the right action or attitude towards others. How should one act in a certain situation?
Is it the right thing to do in life to simply follow the Golden Rule? "Do unto others as you would wish to have them do unto you." Prima facie, this seems perfectly acceptable. But, then, how should a masochist act to others? Should he go around and hurt them, since he would gain pleasure by being hurt?
That dismissal of a traditional and parsimonious answer to one of the deepest questions of life sparks the interest in many. How then, should we act, if not in accordance with the Golden Rule, the traditional layman's Western and Judeo-Christian guideline?
The Three Branches 
Ethics can be divided into three branches that have been developed and elaborated upon throughout the history of philosophy.
Deontology focuses on the importance of the action itself, as opposed to the consequence. Immanual Kant (see Phil 4007) is the father of one of the most popular types of deontology, appropiately named Kantianism.
Kant's philosophy, and most deontology would most closely resemble the Golden Rule. Deontological ethical guidelines could be, for example, "Never lie," "Never steal," "Never kill," "Give to the poor," etc. Note that the emphasis is placed on the prohibition or encouragement of the action itself. The distinction will become clearer soon.
Virtue ethics 
Virtue ethics, the least popular branch of ethics, attempt to instill certain qualities in the person. For example, "Be honest," "Be trustworthy," and "Be nice." The examples are not meant to be vague, but are meant to illustrate that the guidelines are rules more centrally for what kind of person you should be. From there, you can extrapolate likely actions and prohibitions: "An honest person does not lie," or, "A nice person does not hurt or insult his fellow men without proper justification."
Virtue ethics can be found in the teachings of Socrates(reference?) and Aristotle(reference?), who taught their pupils to live the good life through fostering these admirable virutes. In Plato's Republic, Socrates compares the virtues of a person to the composition of a state. The virtuous individual, he says, is temperate, passionate, brave, just and wise.
A recent return of virtue ethics since the 1960's has created a surfeit of apologists for this once-overlooked branch of ethics and given rise to the doctrine of Neo-Aristotelian and Neo-Socratic ethics.
Consequentialism, as the name suggests, encourages actions based solely upon the consequences of the actions. The most popular form of consquentialism is utilitarianism. That is, the individual should act to create the greatest amount of "utility" for the community.
Jeremy Bentham is the father of "Classical" Utilitarianism, though Chinese philosophers had made reference to utility and David Hume was the first to use the word "utility" when decribing ethics.
Kantianism and the Nazis at the door 
A popular critique of strict Kantianism — that is, "Never lie," — is that, if a person harboring Jews during the Holocaust was asked by a Nazi footman about the contents of his attic or cellar, he would have to answer that the was indeed hiding Jews. At least, if he was asked a direct question about the presence of any people, he would not be allowed to lie.
It should be noted that this is the strictest brand of Kantianism, and that many such revisions have since been made since Kant's original writings to the theory. For example, "Act in accordance with these rules unless it would lead to the harm of an individual."
Advanced Topics 
Questions at the deeply critical level, such as "What do we mean by 'right' and 'good' and 'harm'?" are included in the field of meta-ethics (and value theory'). Meta-ethics can be thought to exist at a level above ethics, asking questions like, "What is ethics itself?"