Moral Realism asserts that moral properties exist independently of human minds and are objective truths.

Moral Non-Realism maintains that moral properties are subjective and depend on individual beliefs, attitudes, or emotions.

Immanuel Kant is widely regarded as a prominent proponent of Moral Realism.

David Hume's 'A Treatise of Human Nature' presents a critique of Moral Realism, arguing that moral distinctions arise from sentiments and emotions rather than objective facts.

Moral Realists often appeal to the existence of moral intuitions, which are innate and universal moral beliefs, as evidence for the objectivity of moral properties.

Moral Non-Realists often point to the wide variation in moral beliefs across different cultures and historical periods as evidence against the objectivity of moral properties.

Moral Realists argue that despite the apparent diversity of moral beliefs, there are fundamental moral principles that are shared across cultures, suggesting an underlying moral reality.

Moral Relativism asserts that moral properties are relative to the beliefs, values, and norms of particular cultures or individuals.

Moral Relativists maintain that the rightness or wrongness of an action is determined by the moral standards and values accepted within a particular culture or society.

Alasdair MacIntyre's 'After Virtue' is a notable work in which he argues for a form of Moral Relativism based on the idea of incommensurable moral traditions.

Moral Realists argue that Moral Relativism leads to a situation where there are no objective moral truths and all moral judgments are equally valid, which undermines the possibility of making meaningful moral distinctions.

Moral Nihilism posits that there are no objective moral properties and that all moral judgments are ultimately meaningless and without foundation.

Moral Nihilists maintain that moral statements are neither objectively true nor false, but rather are devoid of any truth value.

Friedrich Nietzsche is widely regarded as a prominent proponent of Moral Nihilism.

Moral Nihilists often argue that since there is no scientific evidence to support the existence of objective moral properties, it is reasonable to conclude that such properties do not exist.