Moral relativism is the view that moral truths are not universal but relative to a culture, society, or individual. Descriptive relativism is the empirical observation that moral beliefs vary across cultures; normative (or metaethical) relativism is the further claim that this variation means there is no fact of the matter beyond what a given group endorses. Individual subjectivism holds that moral claims express or report the attitudes of the speaker. The main challenge to relativism is the argument from moral progress: if morality is merely relative, we cannot say that abolishing slavery was genuine moral improvement, only a change in convention.
Distinguish descriptive relativism (which is true and uncontroversial) from normative relativism (which is philosophically contested). Practice spotting when people use the descriptive observation as an argument for the normative conclusion—this is a common conflation.
From your study of metaethics, you know that moral claims can be analyzed in terms of what kind of thing they are — are they truth-apt beliefs, expressions of attitude, or reports of social conventions? Moral relativism is one answer to that foundational question. The starting point is descriptive relativism: the empirical observation that different cultures endorse different moral norms. Greeks approved of infanticide under certain conditions; many modern societies do not. This sociological fact is genuine and largely uncontested.
The philosophical move — and the contested one — is from descriptive to normative (metaethical) relativism: the inference that because moral beliefs vary, there is no objective moral truth beyond what a group or individual happens to endorse. This inference is not valid on its face. Scientific beliefs also vary across cultures and history, yet we do not conclude that there are no scientific facts. The hard work is in explaining why moral variation should have different implications than scientific variation.
Individual subjectivism goes further: it locates moral truth not in cultural consensus but in the attitudes of the individual speaker. On this view, "cruelty is wrong" means something like "I disapprove of cruelty" — a report of personal attitude rather than a fact about the world. Notice that this makes moral disagreement somewhat puzzling: if you say "cruelty is wrong" and I say "cruelty is not wrong," we aren't actually contradicting each other on subjectivism — we're just reporting different attitudes.
The most powerful objection to relativism is the argument from moral progress. If morality is merely what a culture endorses, then the abolition of slavery wasn't a moral improvement — it was simply a change in convention, no different from changing a dress code. Moral progress requires a standard that transcends convention, against which we can measure whether things genuinely got better. Relativists can respond by defining progress internally (closer adherence to one's own stated values, greater consistency) but critics argue this misses what we actually mean when we say history got things wrong.
Understanding relativism requires keeping the descriptive-normative gap clearly in view at all times. Many everyday arguments slide from "people disagree about X" to "therefore there is no fact about X" — a move that would be rejected instantly in almost every other domain. Whether that inference is any better in ethics is the live question. Relativism forces the objectivist to explain what moral facts are and how we could come to know them; but the relativist faces equally serious questions about how to account for moral disagreement, moral progress, and the phenomenology of moral conviction.
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