Definition
The Is-Ought Gap (or Hume’s Guillotine) is the distinction between factual descriptions of the world (“is”) and normative claims about what should be valued or done (“ought”). David Hume argued that one cannot logically deduce a moral imperative from a natural fact.
Why It Matters
This is the ultimate warning against “naturalistic” ethics. Just because something is a certain way (e.g., survival of the fittest) doesn’t mean it should be that way, protecting our moral agency from being dictated by cold biological facts.
Core Concepts
- Fact vs. Value: Knowing everything about the physical state of the universe (facts) does not tell you how the universe should be arranged (values).
- The Orthogonality Thesis (AI): Stuart Russell and Nick Bostrom use the is-ought gap to prove that a machine’s intelligence (its ability to process facts) is independent of its goals (its values). A superintelligence will not “naturally” become moral just by knowing more facts.
- The Observation Problem: A machine can observe human behavior (facts), but it cannot directly observe human values (oughts). It must infer the “ought” from the “is,” which is inherently noisy and uncertain.