 G.E. Moore’s Principia Ethica of 1903 is often considered a revolutionary work that set a new agenda for 20th-century ethics. This historical view is, however, somewhat overstated. In metaethics Moore’s non-naturalist realism was close to that defended by Henry Sidgwick and other late 19th-century philosophers such as Hastings Rashdall, Franz Brentano, and J.M.E. McTaggart; in normative ethics his ideal consequentialism likewise echoed views of Rashdall, Brentano, and McTaggart. But Principia Ethica presented its views with unusual force and vigor. In particular, it made much more of the alleged errors of metaethical naturalism than Sidgwick or Rashdall had, saying they vitiated most previous moral philosophy. For this reason, Moore’s work had a disproportionate influence on 20th-century moral philosophy and remains the best-known expression of a general metaethical view also shared by later writers such as H.A. Prichard, W.D. Ross, and C.D. Broad.