Ethical Subjectivism holds that there are no objective moral properties and that ethical statements are in fact arbitrary because they do not express immutable truths. Instead, moral statements are made true or false by the attitudes and/or conventions of the observers, and any ethical sentence just implies an attitude, opinion, personal preference or feeling held by someone. Thus, for a statement to be considered morally right merely means that it is met with approval by the person of interest. Another way of looking at this is that judgments about human conduct are shaped by, and in many ways limited to, perception.

An Ethical Subjectivist would argue that the statement "Stalin was evil" expresses a strong dislike for the sorts of things that Stalin did, but it does not follow that it is true (or false) that Stalin was in fact evil. Another person who disagrees with the statement on purely moral grounds (while in agreement with all non-evaluative facts about Stalin) is not making an intellectual error, but simply has a different attitude.

It is compatible with Moral Absolutism, in that an individual can hold certain of his moral precepts to apply regardless of circumstances, but it is also compatible with Moral Relativism in the sense that the truth of moral claims is relative to the attitudes of individuals. Unlike many of the other variants of Moral Anti-Realism, it is a cognitivist theory, in that it holds that ethical sentences, while subjective, are nonetheless the kind of thing that can be true or false, depending on whose approval is being discussed. It stands in contrast to Moral Realism (under which ethical statements are independent of personal attitudes).

Ethical Subjectivism has the advantage of providing a simple, common-sense explanation of what morality is. Even if ethical views often have the internal appearance of objectivity (it feels like we are making, or attempting to make, an objective statement), that would not make them so: it would only mean that people believed them to be fact-stating, due to the assertive nature of most ethical statements. This is further complicated by the fact that ethical claims very often have some implied factual implications (e.g. "Mary is a good person" is likely, although not necessarily, to be based on certain facts about the good things Mary tends to do).

However, Ethical Subjectivism presents a problem in that it offers no way for the parties engaged in ethical debate to resolve their disagreements, merely requiring each side to exercise tolerance by acknowledging the equally factual truth of the perceptions asserted by opponents. This effectively skirts the type of dilemmas that ethics seeks to resolve, namely deciding what is the right thing to do. Another problem is that feelings and attitudes often change over time, as knowledge, experience and circumstances change, which does not make a good base for ethical decisions.

There are several different variants which can be considered under the heading of Ethical Subjectivism:

• Simple Subjectivism: the view (largely as described above) that ethical statements reflect sentiments, personal preferences and feelings rather than objective facts.
• Individualist Subjectivism: the view (originally put forward by Protagoras) that there are as many distinct scales of good and evil as there are individuals in the world. It is effectively a form of Egoism, which maintains that every human being ought to pursue what is in his or her self-interest exclusively.
• Moral Relativism (or Ethical Relativism): the view that for a thing to be morally right is for it to be approved of by society, leading to the conclusion that different things are right for people in different societies and different periods in history.
• Ideal Observer Theory: the view that what is right is determined by the attitudes that a hypothetical ideal observer (a being who is perfectly rational, imaginative and informed) would have. Adam Smith and David Hume espoused early versions of the Ideal Observer Theory, and Roderick Firth (1917 - 1987) is responsible for a more sophisticated modern version.