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Thinker · 1873 CE–1958 CE

G. E. Moore

Moore argued in "Principia Ethica" (1903) that goodness is a simple, indefinable, non-natural property, so that any attempt to define it in terms of natural properties like pleasure commits what he called the naturalistic fallacy. Against philosophical skepticism and idealism, he defended common-sense realism, most famously in "Proof of an External World" (1939), where he held up his hands as evidence that external objects exist.

Intellectual setting

Moore wrote alongside Bertrand Russell in the early 1900s revolt against the British Idealism of Bradley and McTaggart then dominant at Cambridge and Oxford, helping to establish the concern for clarity, common sense, and careful analysis that came to define analytic philosophy.

Key ideas

The naturalistic fallacy and the indefinability of good

Moore argued that "good" names a simple, unanalyzable property that cannot be defined in terms of any natural property such as pleasure or desire-satisfaction, and that every attempt to do so remains open to his "open question" test, which shows the definition incomplete.

The proof of an external world

Against skeptical and idealist arguments that the existence of external objects cannot be proven, Moore argued that holding up his hands and asserting "here is one hand, and here is another" satisfies every reasonable standard of proof, shifting the burden onto skeptical premises rather than common-sense certainties.

Legacy

Moore's "Principia Ethica" shaped the ethical outlook of the Bloomsbury Group and set the terms for twentieth-century metaethical debate over naturalism, and his defense of common sense against skepticism and idealism, alongside Russell, helped found the analytic tradition.