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The Naturalistic Fallacy

Julia Tanner

The naturalistic fallacy is a source of much confusion. In what follows I will explain what G.E. Moore meant by the naturalistic fallacy, give modern day examples of it then mention some of the different types of views it has spawned. Finally, I will consider a few criticisms of it.

I. What is the Naturalistic Fallacy?

Defining Good

Much ink has been spilt over what 'good'; is. The different definitions are too numerous to mention here but some of the common ones include naturalness, happiness, normalness, virtue, and performing one's duty.

The philosopher G. E. Moore (1873-1958) argued that it is a mistake to try and define the concept 'good' in terms of some natural property.[1] He called this mistake the naturalistic fallacy.

The Naturalistic Fallacy in brief

Defining the concept 'good', Moore argued, is as impossible as defining 'yellow';. Yellow is a simple concept. It is simple in that it cannot be defined in terms of any other concept (for instance green). Yellow is yellow, that is as far as one can get when trying to define it. Just so with good. Good cannot be defined or analysed. To do so, to define good as anything other than itself is, therefore, to commit the "naturalistic fallacy".

Moore's project

To understand what the naturalistic fallacy is and the significance it had for Moore it helps to understand his wider project. Moore's project in Principia Ethica is to analyse the concept of good. [2] The result of his analysis is that good is simple, indefinable and unanalysable. [3] If good cannot be defined it cannot be defined as anything other than itself. To do so is, Moore thinks, to commit a particular kind of mistake (one he called the naturalistic fallacy).

Good is simple, indefinable and unanalysable

What does Moore mean by saying that good is simple and indefinable? Moore argues that good is a simple notion in the same way yellow is a simple notion. The notion of yellow cannot be explained fully to anyone who does not already know of it, the same applies to good. [4] Complex objects can be defined by listing their parts and the relationships between those parts. For example, it is possible to define a horse because a horse has many different properties and qualities, all of which can be listed. But it remains the case that once the horse has been reduced to its simplest terms those simple terms cannot be defined. Like all simple terms, they cannot be explained to anyone who does not already know of them. Yellow and good are not complex; they are simple notions. This is the sense in which Moore thinks good is indefinable.

Another important feature of good that Moore wishes to stress is that it is unanalysable. To say that something is unanalysable is simply to say that there is no other way (without using synonyms) of expressing it.

The Open Question argument

Moore defends his claim that good is simple and indefinable through what has come to be known as the open question argument. He argues that it can be shown that good cannot be defined by considering the fact that "whatever definition be offered, it may be always asked, with significance, of the complex so defined, whether it is itself good". [5] For example, it may be argued that good means doing what is pleasurable. And that eating meat is pleasurable and so good (this was not an example that Moore himself used). Initially this may seem a plausible definition of good. But it can still be asked "Is it good to do what is pleasurable?" This question is as intelligible as the original question "Is eating meat good?" Thus, it remains an open question whether or not eating meat is good, regardless of whether it is pleasurable (hence the name the open question argument). Similarly, it may be said that what makes something good is that it is rational. But it can always be asked with significance if it is this which makes it good (and the same could be said of any other property one wishes to replace rationality with). Thus good cannot be defined by anything other than itself.

Moore contends that the same argument adequately demonstrates that the idea that good is meaningless can be rejected. If we consider the question "is pleasure good?" we are not merely wondering if pleasure is pleasant. The notion of good and the notion of pleasure are distinct. Everyone understands the question "Is this good?" [6] This question has a distinct meaning, though it may not be obvious in what manner it is distinct.

Moore acknowledged that the open-question argument does not show that something like pleasure or naturalness cannot be the only criterion for an action's goodness. All that it shows is that a fact about what is pleasant or what is natural, if such facts can be established, cannot be known simply by checking the definition of good. If what is good is to be known at all it must be known in another way.

The Naturalistic Fallacy

These arguments aim to establish the nature of the naturalistic fallacy. If good is simple, indefinable and unanalysable, if what is good remains an open question then to try and define good as anything else is to commit the naturalistic fallacy. [7] The naturalistic fallacy consists in identifying the simple notion of good with some other (naturalistic) notion.

To make the naturalistic fallacy clearer Moore draws an analogy with yellow. Some may try to define 'yellow' by describing its physical equivalent; namely, light waves that stimulate the normal eye. But these light waves are not yellow.

A mistake of this kind is commonly made about good. It may be true that all things that are good are also something else, just as it is true that all things that are yellow will have certain other properties. Ethics aims at discovering which properties it is that all good things have in common. [8] But, Moore argues, many philosophers have thought that when they name those properties they are actually defining good.

II. Some modern day examples of the Naturalistic Fallacy

The naturalistic fallacy is, arguably, committed in everyday life. It is committed when anyone attempts to define good as anything other than itself. Here are a few examples (though not necessarily ones Moore would have used).


One of the most ubiquitous examples of the naturalistic fallacy involves evolution. Some people talk as if they think that that which has evolved is the same thing as being good. Thus, for instance, capitalism may be justified on the basis that it is merely an expression of "the survival of the fittest" and "the survival of the " is good. To make such an argument is, according to Moore, to commit the naturalistic fallacy because good has been defined as something other than itself, as the "the survival of the fittest".


Those who condemn homosexuality often commit the naturalistic fallacy. They say that homosexuality ought to be condemned on the grounds that it is not normal because what is normal is good. But if Moore is right it can still be asked with significance "Is what is normal good?" As such whether what is normal is good (and the goodness of homosexuality) remains an open question and to think it does not is to commit the naturalistic fallacy.

Meat eating

Similarly, those who defend eating meat often commit the naturalistic fallacy when they conflate naturalness with goodness. Their arguments usually run something like this: what is natural is good, it is natural to eat meat therefore it is good to eat meat. But it can still meaningfully be asked "is what is natural good?" This question always remains comprehensible. If it were true that being natural is good then, Moore would argue, it would be pointless to ask whether it is good because the answer would be obvious. But as it stands whether what is natural is good remains an open question (thus so does the goodness of eating meat).

III. Objections to the Naturalistic fallacy

Not all philosophers agree that the naturalistic fallacy really is a fallacy or that the open question argument works. Here are some of the most common objections.

It may be objected that it is not clear what saying good is a simple notion means. [9] When Moore says that good is indefinable what he means is that it is what it is and not anything else (it cannot be defined by reference to anything else). And this idea is not as obscure as it may at first appear. There are other concepts that we take to be basic like good. For instance, colour cannot be defined. One may object that one can point to a colour like yellow and say this is a colour. But this would be wrong, yellow is an instance of colour. It is not colour itself. Such concepts cannot be defined and it is a mistake to suppose, as is often the case, that by pointing to an instance of the concept that it has been defined. To point to something that is good is not to define good. Moore's main claim here is that good defies a certain kind of definition.

Moore is arguing that good is a basic ethical concept from which all other ethical concepts must be derived. Moore distinguishes good from what has good. Good is the predicate good (a simple concept). What has good is that which possesses the predicate good. [10] Good is indefinable. What is good can, however, be defined. Thus while one cannot define what good is one can say which particular things are good.

Criticisms of the idea that good is simple, natural and unanalysable

Fred Feldman does not think that it is good enough to say good is indefinable, "[m]etaphors... and enforced silences will not help us to understand [good]". [11] He argues that to say good is indefinable not only adds to the confusion but strengthens the case against it. Feldman insists that it is reasonable to demand clarity as the concept is so important in moral philosophy.

But Moore was not arguing that good is an elusive concept that is hard to pin down. This is not what Moore means when he says that good cannot be defined. The important claim he wants to make is not that nothing significant can be said about the concept of good but rather that the concept cannot be defined by identifying it with any individual property. Moore argued that a significant mistake is often made (the naturalistic fallacy) whereby good is said to be some property, for example happiness. By saying good is indefinable Moore is simply trying to guard against this mistake.

The naturalistic fallacy is mere tautology

In the Preface To The Second Edition Moore expresses concern that the Naturalistic Fallacy may be seen as little more than a tautology for obviously it is true to say that good is good and nothing else. [12] But the Naturalistic Fallacy has more significance than this. Moore is correct that people often ignore this tautology and say that good "is" some other concept or property. If it is the fallacy Moore thinks it is then it is an important and prevalent one which it is appropriate to point out and name it in order to avoid its being made in the future.

Naturalist objections

Some naturalists have argued that ethical terms, such as good can be defined in non-ethical natural terms. They think that ethical judgements directly follow from facts (like what human nature is like). These philosophers deny that the naturalistic fallacy is a fallacy and they think it is possible to argue from a fact to a value. They doubt that facts really do stand in opposition to values; that there is a fact-value distinction. For instance, a utilitarian would hold that the goodness of an action is identical to the happiness it promotes (a straightforward running together of facts and values).

IV. Summary and conclusion

If Moore's Naturalistic Fallacy is a fallacy then we need to take a great deal more care about how we discuss good. If Moore is right then there are important implications both for the way we discuss good at a theoretical level and how we discuss practical ethics. At the theoretical level, if Moore is right then we cannot define good and any attempt to do so is a mistake. At the practical level we need to think a lot more carefully about many of the arguments we make about what is good or right. If we base such arguments on the idea that good is some property such as naturalness then many of the arguments people make are simply false (such as those above) and we need to look for others to replace them.

There are, of course, many philosophers who think that the naturalistic fallacy is not a fallacy. Whether it is or not requires a great deal of thought (hopefully the further reading below should help you to make your mind up).

Julia Tanner
University of Durham

Further Reading

Introductory texts:
Benn, Piers 2002: Ethics. London: Routledge.
Pojman, Louis P. 2002: Ethics: Discovering Right and Wrong. Ontario: Wadsworth.
Warburton, Nigel 1995: Philosophy: The Basics. London: Routledge.

Non-introductory texts:
Ayer, A. J. 1949: Language, Truth and Logic. London.
Feldman, Fred 1998: "Hyperventilating about Intrinsic Value" The Journal of Ethics 2.
Frankena W. K. 1939: "The Naturalistic Fallacy", Mind, New Series, Vol. 48, No. 192 (Oct., 1939), pp. 464-477.
Hare, R. M. 1952: The Language of Morals. Oxford: The Clarendon Press.
Hudson, W. D. (ed.) 1969: The Is/Ought Question. London.
Hume, David 1975: An Enquiry Concerning the Principles of Morals, in Enquiries Concerning Human Understanding and Concerning the Principles of Morals in Selby-Bigge, L. A . (ed.). Oxford: Oxford University Press.
Moore, G. E. 1993: Principia Ethica. Cambridge: Cambridge University Press.
Nowell-Smith, P. H. 1954: Ethics. London: Penguin, pp. 40-2.
Searle, John. R. 1964: "How to derive "ought" from "is"" Philosophical Review, pp.43-58.
Smith, Tara 1998: "Intrinsic Value: Look-Say Ethics" The Journal of Value Inquiry 32, pp. 539-553.
Wiggins, David 1987: "Truth, Invention and the Meaning of Life" in Needs, Values, Truth. London: Blackwell.


[1]  G. E. Moore was an English philosopher. He was educated and taught at the University of Cambridge. With Gottlob Frege, Ludwig Wittgenstein, and Bertrand Russell he helped found the Analytic tradition in philosophy. Moore is best known, however, for his defence of ethical non-naturalism and naturalistic philosophy.  [back] 

[2]  Moore, G. E. 1993: Principia Ethica. Cambridge: Cambridge University Press. p. 55.  [back] 

[3]  Moore 1993, p. 58.  [back] 

[4]  Moore 1993, p. 58.  [back] 

[5]  Moore 1993, p. 67.  [back] 

[6]  Moore 1993, p. 68.  [back] 

[7]  Moore 1993, p. 62  [back] 

[8]  Moore spends most of Principia Ethica trying to avoid the naturalistic fallacy and discuss which things he thinks possess intrinsic value (goodness), and the kinds of actions we ought to perform.  [back] 

[9]  Smith, Tara 1998: "Intrinsic Value: Look-Say Ethics" The Journal of Value Inquiry 32, pp. 539-553.  [back] 

[10]  Moore 1993, p. 60.  [back] 

[11]  Feldman, Fred 1998: "Hyperventilating about Intrinsic " The Journal of Ethics 2, p. 340.  [back] 

[12]  The Preface to the Second Edition was written in 1922 but abandoned unfinished.  [back]