We all know that certain acts are morally wrong: murder, theft, slander and kidnapping. We also know that certain acts are morally right: helping the poor, healing the sick, educating the ignorant and freeing slaves. But there are other issues that are not nearly so clear. These gray areas include the environment, gun control and government regulations in general. In addition to these problems, there is no agreed method or common understanding that would resolve the problem.
The first step to understanding ethics is by understanding what ethics is. We might assume that ethics is limited to moral rules. There would be rules against kinds of action, requiring types of action and permitting kinds of action. But this is not true. Moral virtues are not moral rules, but they do belong within ethics. Someone who is courageous is someone who is disposed to act correctly in situations requiring courage. Perhaps ethics is an understanding of right and wrong. But right and wrong cannot be understood apart from what is good. Goodness is what right acts aim at and bad or wrong acts are contrary to it. This means that ethics is about goodness.
Ethics is not a theoretical discipline but an active one. The whole point of ethics is living well. We want to know how to avoid bad acts, do what is right and be happy. But the nature of the subject ensures that there will be a lot of discussion of relatively obscure topics. For example, the CIA faces unique moral dilemmas that do not apply to ordinary citizens. So a discussion of ethics that includes rare circumstances will require plenty of theoretical insight. This does not change the fact that ethics is an active science. Since ethics is about goodness and active sciences are about action, ethics is an active science aiming at good action.
The second step to understand ethics is by understanding the current controversies. There are so many controversies that it is impossible to fairly list all of them without dividing ethics. Currently ethics is divided into normative ethics, metaethics and various practical ethics. Since they are all kinds of ethics, they must all be active sciences aimed at doing what is good. Normative ethics determines what is good. For example, whether or not it is ever good to lie. Metaethics determines what goodness is. Finally, applied ethics takes a particular normative ethic and asks how this applies to a particular active science. For example, bioethics asks what is ethical in the particular situations of the health sciences. Normative and applied ethics both ask what is good but normative ethics asks this question generally and practical ethics asks it specifically.
The controversies that properly exist at the level of ethics are ones that cannot be put into the current categories of ethics. Such controversies would be ones about the definition of ethics or the definitions of the various divisions of ethics. Since there are no such controversies, we can proceed to the final step of understanding ethics. This last step is understanding what each division of ethics is and discusses.