In Philosophy, Ethics is commonly divided into two branches, normative ethics and meta-ethics. Normative ethics addresses questions such as "What actions are good and bad?" and "What should we do?" Thus, a theory of normative ethics will endorse some ethical evaluations. Meta-ethics, on the other hand, seeks to understand the nature of ethical evaluations. Thus, examples of meta-ethical questions include:
- What does it mean to say something is "good"?
- How, if at all, do we know what is right and wrong?
- How do moral attitudes motivate action?
- Are there objective values?
In the last century, the field of meta-ethics has been dominated by five kinds of theories:
- Ethical intuitionism, which holds that there are objective, irreducible moral properties (such as the property of 'goodness'), and that we sometimes have intuitive awareness of moral properties or of moral truths.
- Ethical naturalism, which holds that there are objective moral properties, but that these properties are reducible. Most ethical naturalists hold that we have empirical knowledge of moral truths. Several have argued that moral knowledge can be gained by the same means as scientific knowledge.
- Ethical subjectivism, which holds that moral statements are made true or false by the attitudes and/or conventions of observers. An example of this is the view that for a thing to be morally right is just for it to be approved of by society; this leads to the view that different things are right in different societies.
- Non-cognitivism, which holds that ethical sentences are neither true nor false because they do not assert genuine propositions. Some have held that ethical sentences such as "Stealing is wrong" are merely expressions of emotion; others have argued that they are more like imperatives.
- Moral skepticism, which holds that ethical sentences are generally false. Moral skeptics hold that there are no objective values, but that the claim that there are objective values is part of the meaning of ordinary ethical sentences; that is why, in their view, ethical sentences are false.