Naturalistic fallacy

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In philosophical ethics, the term "naturalistic fallacy" was introduced by British philosopher G. E. Moore in his 1903 book Principia Ethica.[1] Moore argues it would be fallacious to explain that which is good reductively in terms of natural properties such as "pleasant" or "desirable".

Moore's naturalistic fallacy is closely related to the is–ought problem, which comes from Hume's Treatise. However, unlike Hume's view of the is–ought problem, Moore (and other proponents of ethical non-naturalism) did not consider the naturalistic fallacy to be at odds with moral realism.

The phrase "naturalistic fallacy" can also be used to refer to the fallacious appeal to nature, a mistaken claim that something is good or right because it is natural (or bad or wrong because it is unnatural). See below.

Different common uses

The is–ought problem

The term "naturalistic fallacy" is sometimes used to describe the deduction of an "ought" from an "is" (the is–ought problem).[2]

In using his categorical imperative Kant deduced that experience was necessary for their application. But experience on its own or the imperative on its own could not possibly identify an act as being moral or immoral. We can have no certain knowledge of morality from them, being incapable of deducing how things ought to be from the fact that they happen to be arranged in a particular manner in experience.

Bentham, in discussing the relations of law and morality, found that when people discuss problems and issues they talk about how they wish it would be as opposed to how it actually is. This can be seen in discussions of natural law and positive law. Bentham criticized natural law theory because in his view it was a naturalistic fallacy, claiming that it described how things ought to be instead of how things are.

Moore's discussion

The title page of Principia Ethica

According to G. E. Moore's Principia Ethica, when philosophers try to define "good" reductively in terms of natural properties like "pleasant" or "desirable", they are committing the naturalistic fallacy.

...the assumption that because some quality or combination of qualities invariably and necessarily accompanies the quality of goodness, or is invariably and necessarily accompanied by it, or both, this quality or combination of qualities is identical with goodness. If, for example, it is believed that whatever is pleasant is and must be good, or that whatever is good is and must be pleasant, or both, it is committing the naturalistic fallacy to infer from this that goodness and pleasantness are one and the same quality. The naturalistic fallacy is the assumption that because the words 'good' and, say, 'pleasant' necessarily describe the same objects, they must attribute the same quality to them.[3]

— Arthur N. Prior, Logic And The Basis Of Ethics

In defense of ethical non-naturalism, Moore's argument is concerned with the semantic and metaphysical underpinnings of ethics. In general, opponents of ethical naturalism reject ethical conclusions drawn from natural facts.

Moore argues that good, in the sense of intrinsic value, is simply ineffable: it cannot be defined because it is not a natural property, being "one of those innumerable objects of thought which are themselves incapable of definition, because they are the ultimate terms by reference to which whatever is capable of definition must be defined".[4] On the other hand, ethical naturalists eschew such principles in favor of a more empirically accessible analysis of what it means to be good: for example, in terms of pleasure in the context of hedonism.

That "pleased" does not mean "having the sensation of red", or anything else whatever, does not prevent us from understanding what it does mean. It is enough for us to know that "pleased" does mean "having the sensation of pleasure", and though pleasure is absolutely indefinable, though pleasure is pleasure and nothing else whatever, yet we feel no difficulty in saying that we are pleased. The reason is, of course, that when I say "I am pleased", I do not mean that "I" am the same thing as "having pleasure". And similarly no difficulty need be found in my saying that "pleasure is good" and yet not meaning that "pleasure" is the same thing as "good", that pleasure means good, and that good means pleasure. If I were to imagine that when I said "I am pleased", I meant that I was exactly the same thing as "pleased", I should not indeed call that a naturalistic fallacy, although it would be the same fallacy as I have called naturalistic with reference to Ethics.

— G. E. Moore, Principia Ethica § 12

In §7, Moore argues that a property is either a complex of simple properties, or else it is irreducibly simple. Complex properties can be defined in terms of their constituent parts but a simple property has no parts. In addition to "good" and "pleasure", Moore suggests that colour qualia are undefined: if one wants to understand yellow, one must see examples of it. It will do no good to read the dictionary and learn that "yellow" names the colour of egg yolks and ripe lemons, or that "yellow" names the primary colour between green and orange on the spectrum, or that the perception of yellow is stimulated by electromagnetic radiation with a wavelength of between 570 and 590 nanometers, because yellow is all that and more, by the open question argument.

Bernard Williams called Moore's use of the term 'naturalistic fallacy' a "spectacular misnomer", the question being metaphysical, as opposed to rational.[5]

Appeal to nature

Some people use the phrase "naturalistic fallacy" or "appeal to nature" to characterize inferences of the form "Something is natural; therefore, it is morally acceptable" or "This property is unnatural; therefore, this property is undesireable." Such inferences are common in discussions of homosexuality, environmentalism, and veganism.

The naturalistic fallacy is the idea that what is found in nature is good. It was the basis for social Darwinism, the belief that helping the poor and sick would get in the way of evolution, which depends on the survival of the fittest. Today, biologists denounce the naturalistic fallacy because they want to describe the natural world honestly, without people deriving morals about how we ought to behave (as in: If birds and beasts engage in adultery, infanticide, cannibalism, it must be OK).


Some philosophers reject the naturalistic fallacy and/or suggest solutions for the proposed is–ought problem.

Sam Harris argues that it is possible to derive "ought" from "is", and even that it has already been done to some extent.[7][8] He sees morality as a budding science. This view is critical of Moore's "simple indefinable terms" (which amount to qualia), arguing instead that such terms actually can be broken down into constituents.

Ralph McInerny suggests that "ought" is already bound up in "is", in so far as the very nature of things have ends/goals within them. For example, a clock is a device used to keep time. When one understands the function of a clock, then a standard of evaluation is implicit in the very description of the clock, i.e., because it "is" a clock, it "ought" to keep the time. Thus, if one cannot pick a good clock from a bad clock, then one does not really know what a clock is. In like manner, if one cannot determine good human action from bad, then one does not really know what the human person is.[9]

Certain uses of the naturalistic fallacy refutation (a scheme of reasoning that declares an inference invalid because it incorporates an instance of the naturalistic fallacy) have been criticised as lacking rational bases, and labelled anti-naturalistic fallacy.[10] For instance, Alex Walter wrote:

"The naturalistic fallacy and Hume’s ‘law’ are frequently appealed to for the purpose of drawing limits around the scope of scientific inquiry into ethics and morality. These two objections are shown to be without force."[11]

The refutations from naturalistic fallacy defined as inferring evaluative conclusions from purely factual premises[12] do assert, implicitly, that there is no connection between the facts and the norms (in particular, between the facts and the mental process that led to adoption of the norms).

See also


  1. Moore, G.E. Principia Ethica § 10 ¶ 3
  2. W. H. Bruening, "Moore on 'Is-Ought'," Ethics 81 (January 1971): 143-9.
  3. Prior, Arthur N. (1949), Chapter 1 of Logic And The Basis Of Ethics, Oxford University Press (ISBN 0-19-824157-7)
  4. Moore, G.E. Principia Ethica § 10 ¶ 1
  5. Williams, Bernard Arthur Owen (2006). Ethics and the Limits of Philosophy. Abingdon, Oxfordshire: Taylor & Francis. p. 121. ISBN 978-0-415-39984-5.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  6. Sailer, Steve (October 30, 2002). "Q&A: Steven Pinker of 'Blank Slate'". UPI. Archived from the original on December 5, 2015. Retrieved December 5, 2015. Unknown parameter |dead-url= ignored (help)<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  7. Harris, Sam (29 March 2010). "Moral Confusion in the Name of "Science"". Retrieved 30 March 2011.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  8. Harris, Sam (22 March 2010). "Science Can Answer Moral Questions". Retrieved 30 March 2011.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  9. McInerny, Ralph (1982). Ethica Thomistica. Cua Press. p. Chp. 3.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  10. Casebeer, W. D., "Natural Ethical Facts: Evolution, Connectionism, and Moral Cognition", Cambridge, MA: MIT Press, (2003)
  11. Walter, Alex (2006). "The Anti-naturalistic Fallacy: Evolutionary Moral Psychology and the Insistence of Brute Facts". Evolutionary Psychology. 4: 33–48.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  12. "TheFreeDictionary", naturalistic fallacy<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>.


  • Moore, George Edward (1903). Principia Ethica. Cambridge: Cambridge University Press. ISBN 0-334-04040-X.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>

Further reading

External links