什麼是自然主義謬誤

視「善」（或任何相等的詞語）彷佛它是自然屬性的名稱的謬誤。1903年，摩爾在他的《倫理學原理》（Principia Ethica）一書中提出他的「問題待解的論證」（open-question argument），對抗他所謂的自然主義謬誤，其目的在於證明，「善」是個簡單的、無可分析的性質名稱，它無法以世界上某些自然的性質加以界定，無論它是彌爾所言的「使人感到快樂」，或斯賓塞所言的「高度發展」。因為摩爾的論證應用在任何以其他事物來界定善的嘗試，包括超自然者，如「上帝所願」，因此「自然主義謬誤」一詞並不貼切。問題待解的論證使得任何對善提出的定義都陷入疑難。（舉例來説，「善的意思是使人感到快樂」就變成「是否每一件使人感到快樂的事就是善？」）摩爾的要點是，如果問題是有意義的，則提議的定義就是不正確的，因為如果定義是正確的，則問題將是沒有意義。

naturalistic fallacy

Fallacy of treating the term "good" (or any equivalent term) as if it were the name of a natural property. In 1903 G. E. Moore presented in Principia Ethica his "open-question argument" against what he called the naturalistic fallacy, with the aim of proving that "good" is the name of a simple, unanalyzable quality, incapable of being defined in terms of some natural quality of the world, whether it be "pleasurable" (John Stuart Mill) or "highly evolved" (Herbert Spencer). Since Moore's argument applied to any attempt to define good in terms of something else, including something supernatural such as "what God wills," the term "naturalistic fallacy" is not apt. The open-question argument turns any proposed definition of good into a question (e.g., "Good means pleasurable" becomes "Is everything pleasurable good?")-Moore's point being that if the question is meaningful, the proposed definition cannot be correct, since if it were, the question of would be meaningless.