- Consequentialism -- The results (preferably ALL the results) define the goodness of the action. (Officer: "Are there any jews in this house?" "No"). Note: This category includes both egoist approaches and utilitarian approaches. The only difference is which goal.
- Deontology -- Whether you followed the rules defines the goodness of the action (Don't push the fat guy in front of a train, even to save 5 others, who would have been killed)
- Virtue-ethics -- Actions are relevant to goodness only insofar as they explain what kind of person you are. (The question isn't whether you won or lost the battle...it's whether you were courageous).
It is also important to call out the distinction between two other questions in ethics:
- How do people actually respond ethically? -- This is Jon Haidt's stuff that I like so much. If you look at how people actually respond ethically, you'd do pretty well to model on 6 axes...harm/care, justice/fairness, purity/sanctity, ingroup/loyalty, authority/respect, and liberty/freedom. I'd argue that most of the rest of the rest of ethical disputes come when these axes push in different directions. For instance, sometimes/often fairness/justice pushes against ingroup/loyalty.
- How would be better for people to respond? What ethical system would be net-best for folks. I'm personally a huge fan of David Schmidtz here.
My current thought on the meta-side is that ethics is very simply evolution's way of dodging our conscious mind's feebleness, and building in effective long term strategy. Game theory says that tit-for-two-tats is the appropriate strategy in indefinite duration iterative games with noise (What we really see). Turns out vampire bats play tit-for-two-tats or something very close as well. Justice/fairness and harm/care are awful close to a built-in over-ride for our short-term thinking grey muscles to say--"Yo, Bozo, Be nice"...it's better in the long run.
Similarly, in single-play game theory, it's most effective to defect. Hence...one needs a different strategy for dealing with outgroup folks that one won't be playing with forever. Purity/Sanctity Ingroup/Loyalty and Authority/Respect are about defining the boundaries between ingroup and outgroup.
Finally...intra-group competition may be the single biggest driving factor in top food-chain pack-predator evolution (humans)...and so preserving space for the self to act is essential, which should lead to a built-in liberty/freedom issue.
Summary: Evolution built ethics to make human beings play smart long-term game theory instead of playing stupid short-term game theory, which is all the power their little grey noodles have in them. IF you think you're smarter than evolution...you can screw yourself and several others pretty badly by testing the proposition and finding out you're wrong. Otherwise... behave ethically.
Aside: It seems as if the human ethical position is highly sensitive to power. When in a position of power, folks' ethical opinions change dramatically. This fits my hypothesis positing a game-theoretic evolutionary substitute for the natural human lack of long-term thinking.