Meta-Ethics
Is-Ought Problem
You can't derive an "ought" from an "is" — Hume's gap between fact and value
The is-ought problem (Hume's law) is the philosophical thesis that one cannot logically derive prescriptive (ought) statements from descriptive (is) statements. David Hume (1739) noticed: writers often slip from "is" to "ought" without justification. Pure facts don't entail moral conclusions. Example: "people frequently lie" doesn't imply "people should lie" (or shouldn't). Major issue in meta-ethics. Naturalistic fallacy (G.E. Moore, related): can't define moral terms (good) in natural terms. Implications: ethics not reducible to science; values vs facts. Responses: ethical naturalism (some bridges exist), divine command, contractualism.
- Posed byDavid Hume (1739, Treatise)
- ProblemCan't logically derive "ought" from "is"
- Naturalistic fallacyG.E. Moore (1903); related but distinct
- Open question argumentMoore's argument that good is not natural
- ImplicationFacts ≠ values
- ResponsesEthical naturalism, contractualism, divine command
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Why is-ought matters
- Meta-ethics. Foundation of ethical theory.
- Science and values. Distinguishing description and prescription.
- Evolutionary ethics. Avoiding fallacy.
- Public discourse. Avoiding common error.
- Moral psychology. Understanding moral reasoning.
- Critical thinking. Logical rigor.
- Religion. Divine command theory.
Common misconceptions
- Same as naturalistic fallacy. Related but distinct.
- Settled question. Still debated.
- Implies ethics relativist. Just shows facts ≠ values.
- Hume invented entirely. Earlier discussions; he formalized.
- Easy to spot. Often subtle; hidden.
- Bridges impossible. Need additional premises; not impossible.
Frequently asked questions
What's the is-ought problem?
Hume (1739) noticed: many writers shift from "is" to "ought" without explanation. Example: "Humans are social by nature, therefore we ought to be social." But: how does the description (we are social) entail the prescription (we ought to be social)? Pure facts don't logically yield values. Hume: requires extra "ought" premise to bridge gap. Often: bridging premise unjustified.
What's the naturalistic fallacy?
G.E. Moore (1903). Related but distinct from is-ought. Naturalistic fallacy: defining moral terms (good) in terms of natural properties (pleasure, evolution-favored, etc.). Moore argued: any such definition fails. Open question argument: "is X good?" remains meaningful question for any natural property X. So good ≠ X. Whatever you propose, "is that really good?" is open question.
How are they different?
Is-ought is about logical derivation: can't derive moral from non-moral. Naturalistic fallacy is about definition: can't define moral in natural terms. Often conflated; technically distinct. Both: argue for autonomy of ethics from natural facts. Both: cited by anti-naturalists in meta-ethics.
How does it apply to evolutionary ethics?
Common error: deriving morality from evolution. "Humans evolved to behave X; therefore X is right." Is-ought issue: evolutionary fact doesn't entail moral conclusion. Just because something is adaptive doesn't make it right. Natural may be amoral (parasitism), wrong (rape), or right (cooperation) — depends on independent moral standards. Sociobiology often slips into is-ought fallacy.
How does it affect science and ethics?
Suggests: science can describe but not prescribe. Climate science: tells us climate is changing; doesn't tell us we should act. Need additional moral premises (e.g., we ought to preserve life, future generations matter). Pure science: amoral. Combined with moral framework: actionable. Important: distinguishing factual from normative claims.
What are responses to it?
Several. (1) Ethical naturalism: some bridges exist. Eudaimonist views (Aristotelian flourishing) connect facts about humans to moral conclusions. (2) Divine command: facts about God's commands generate oughts. (3) Constructivism: oughts arise from rational agreement (Rawls, Korsgaard). (4) Error theory: moral claims are all false (no oughts). (5) Bridge principles: independent moral premises bridge gap.
Is the gap real?
Most philosophers think Hume identified important issue. But: not necessarily unbridgeable. Need: additional moral premise. Once accepted, oughts can follow. Gap is logical, not necessarily metaphysical. Some philosophers (Searle): facts can entail values in specific cases (promising creates obligation). Continuing debate. Hume's insight: values can't come purely from facts.