# Principia Ethica — Themes > Major themes in Principia Ethica by G. E. Moore. ## The Naturalistic Fallacy Moore argues that 'good' is a simple, indefinable quality and that attempts to define it in terms of natural properties (like pleasure or desire) commit the 'naturalistic fallacy,' which is the central error in most ethical systems. ### Where it surfaces - [Principia Ethica](https://www.betterreads.dev/discover/principia_ethica_se/chapters/principia-ethica): Moore identifies and argues against the naturalistic fallacy, the error of defining 'good' in terms of natural properties. - [I: The Subject-Matter of Ethics](https://www.betterreads.dev/discover/principia_ethica_se/chapters/i-the-subject-matter-of-ethics): Moore identifies and critiques the fallacy of defining 'good' in terms of natural properties (e.g., pleasure, desire), arguing that 'good' is a simple, indefinable notion. - [II: Naturalistic Ethics](https://www.betterreads.dev/discover/principia_ethica_se/chapters/ii-naturalistic-ethics): Central theme: Moore defines and applies the naturalistic fallacy to critique theories that define 'good' in terms of natural properties like evolution or pleasure. - [III: Hedonism](https://www.betterreads.dev/discover/principia_ethica_se/chapters/iii-hedonism): Moore argues that Hedonism is primarily a form of Naturalistic Ethics, committing the naturalistic fallacy by confusing 'good' with 'pleasure' or 'desired.' - [IV: Metaphysical Ethics](https://www.betterreads.dev/discover/principia_ethica_se/chapters/iv-metaphysical-ethics): Moore argues that metaphysical ethics commits the naturalistic fallacy by inferring ethical conclusions from propositions about reality. ## Intrinsic vs. Instrumental Value The book rigorously distinguishes between things that are good in themselves (intrinsic value) and things that are good as means to an end (instrumental value), arguing that ethical inquiry must first identify what has intrinsic worth. ### Where it surfaces - [Preface to the 1903 Edition](https://www.betterreads.dev/discover/principia_ethica_se/chapters/preface-to-the-1903-edition): Moore distinguishes the question of what things are good in themselves (intrinsic value) from questions about right action. - [I: The Subject-Matter of Ethics](https://www.betterreads.dev/discover/principia_ethica_se/chapters/i-the-subject-matter-of-ethics): Moore distinguishes between things good as ends (intrinsic value) and things good as means, emphasizing that judgments of intrinsic value are universal. - [IV: Metaphysical Ethics](https://www.betterreads.dev/discover/principia_ethica_se/chapters/iv-metaphysical-ethics): Distinguishes between the intrinsic goodness of things and their instrumental value in practical ethics. - [Ethics in Relation to Conduct](https://www.betterreads.dev/discover/principia_ethica_se/chapters/v-ethics-in-relation-to-conduct): Distinguishes between virtue as a means (often lacking intrinsic value) and the intrinsic goodness of certain mental states included in virtue. - [VI: The Ideal](https://www.betterreads.dev/discover/principia_ethica_se/chapters/vi-the-ideal): Moore distinguishes between things that are good in themselves (intrinsic value) and things that are good as means; he identifies personal affections and aesthetic enjoyments as the greatest intrinsic goods. ## The Ideal and Good in Itself Moore explores what constitutes the 'Ideal' or 'Summum Bonum,' arguing that many different things (e.g., personal affection, aesthetic enjoyment) are good in themselves, and that the best state of affairs is a complex whole of such goods. ### Where it surfaces - [Preface to the 1903 Edition](https://www.betterreads.dev/discover/principia_ethica_se/chapters/preface-to-the-1903-edition): Moore announces his intention to identify classes of intrinsic goods and evils in Chapter VI. - [VI: The Ideal](https://www.betterreads.dev/discover/principia_ethica_se/chapters/vi-the-ideal): The chapter defines the ideal as consisting of complex organic unities involving consciousness and emotion, and argues that these are the ultimate ends of human action. ## Ethics of Conduct and Duty Moore separates ethical questions into two kinds: what is good in itself and what actions we ought to perform, asserting that right actions are those that produce the greatest amount of good, making duty a matter of causal consequences. ### Where it surfaces - [Ethics in Relation to Conduct](https://www.betterreads.dev/discover/principia_ethica_se/chapters/v-ethics-in-relation-to-conduct): Moore redefines 'right' and 'duty' in terms of causal consequences, arguing that moral laws are empirical generalizations about producing good effects. ## Critique of Hedonism Moore systematically refutes the hedonistic principle that pleasure is the sole good, using the method of isolation to show that pleasure alone lacks intrinsic value and that valuable wholes often include other elements. ### Where it surfaces - [Principia Ethica](https://www.betterreads.dev/discover/principia_ethica_se/chapters/principia-ethica): Moore critiques hedonistic theories, including those of Mill and Sidgwick, for committing the naturalistic fallacy. - [II: Naturalistic Ethics](https://www.betterreads.dev/discover/principia_ethica_se/chapters/ii-naturalistic-ethics): Moore previews his critique of hedonism, arguing that pleasure cannot be the sole good without committing the naturalistic fallacy. - [III: Hedonism](https://www.betterreads.dev/discover/principia_ethica_se/chapters/iii-hedonism): The entire chapter is a sustained critique of Hedonism, showing its logical flaws and the inadequacy of its arguments. - [Ethics in Relation to Conduct](https://www.betterreads.dev/discover/principia_ethica_se/chapters/v-ethics-in-relation-to-conduct): Acknowledges Hedonists' methodological insight but criticizes their failure to recognize non-hedonic intrinsic goods. ## Metaphysical Ethics and Reality Moore criticizes metaphysical ethical theories (e.g., those of Kant or Hegel) that attempt to derive ethical truths from claims about the nature of reality, arguing that this also commits the naturalistic fallacy by confusing 'what is' with 'what ought to be.' ## Method of Ethical Reasoning The book emphasizes the importance of clarifying questions before answering them, and establishes that fundamental ethical principles (about intrinsic good) are self-evident intuitions, while practical duties require empirical causal evidence. ### Where it surfaces - [Epigraph](https://www.betterreads.dev/discover/principia_ethica_se/chapters/epigraph): The epigraph underscores the importance of precise definitions and logical clarity in ethical reasoning, rejecting equivocation or reductionism. - [Preface to the 1903 Edition](https://www.betterreads.dev/discover/principia_ethica_se/chapters/preface-to-the-1903-edition): Moore emphasizes the need to clearly distinguish questions and identify relevant evidence, laying out his method for ethical inquiry. - [I: The Subject-Matter of Ethics](https://www.betterreads.dev/discover/principia_ethica_se/chapters/i-the-subject-matter-of-ethics): Moore discusses the importance of clear analysis and the principle of organic unities, arguing that the value of a whole is not simply the sum of its parts. - [IV: Metaphysical Ethics](https://www.betterreads.dev/discover/principia_ethica_se/chapters/iv-metaphysical-ethics): Critiques the logical and epistemological methods used by metaphysicians to ground ethics. - [VI: The Ideal](https://www.betterreads.dev/discover/principia_ethica_se/chapters/vi-the-ideal): Moore insists that ethical truths must be discovered by careful examination of instances, not by assuming symmetry or system; he advocates focusing on two clear questions: intrinsic value and means to the best. 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