Naturalistic Fallacy

Benjamin W. McCraw

If the opinion which I have now stated is psychologically true - if human nature is so constituted as to desire nothing which is not either a part of hap­piness or a means of happiness - we can have no other proof, and we require no other, that these are the only things desirable.

John Stuart Mill

Unlike many fallacies - formal or informal - it’s not likely that one will find the naturalistic fallacy in standard logic textbooks. Typically, one can motivate the fallacy via G.E. Moore - the originator of the term “naturalistic fallacy.” For him,

It may be true that all things which are good are also something else... And it is a fact that Ethics aims at discovering what are those other properties belonging to all things which are good. But far too many philosophers have thought that when they named those other properties they were actually defining good; that these properties, in fact, were simply not ‘other,’ but absolutely and entirely the same with goodness. This view I propose to call the ‘naturalistic fallacy’. When a man confuses two natural objects with one another, defin­ing one by the other. then there is no reason to call the fallacy naturalistic.

But if he confuses "good.'' which is not in the same sense a natural object, with any natural object whatever. then there is a reason for calling that a naturalistic fallacy. (2009, 13-14)

Here the point is that natural properties (e.g., pleasure) are logically and/or metaphysically distinct from normative or moral properties (e.g., goodness) and, thus, any identification of a natural property with a normative property would be defective.

Consider the opening quotation by Mill.

Now, why think this maneuver is fallacious? Moore has wider reasons about metaphilosophical commitments to the non-naturalism of moral values. His metaphysical approach disallows a move from natural to non-natural properties (in Moore's language) because he denies that there are any natural objects possessing normative properties at all. Moore's metaphysics of values (metaethics) disallows any movement from natural to non-natural properties. He thinks of normative properties/objects as logically and metaphysically distinct from non-natural properties/objects. Yet if one rejects the wider non-naturalistic moral realism central to Moore's naturalistic fallacy, it seems possible to accept a movement from the natural to normative. The naturalistic fallacy, if this is correct, follows from one's metaphysical (metaethical) com­mitments rather than simply a general defect of reasoning.

For instance, Aristotle (2009) gives the famous “function” argument in Nichomachean Ethics for his account of the ultimate human good (eudaimo- nia). “For just as a flute-player, a sculptor, or any artist, and, in general, for all things that have a function or activity, the good and the ‘well' is thought to reside in the function” (11). Now, this appears to move from the natural/ descriptive (what's the function of X) to the normative (what's the good of X). Yet, it's implausible to think of Aristotle's espousing a non-naturalism a la Moore. On Aristotle's view, a thing's function just is imbued with the norma­tive properties associated with that object. (Philippa Foot's Natural Goodness offers a modern approach entwining natural and normative properties in the ballpark of the interpretation of Aristotle I'm advancing here.) A flute-player's function isn't separate from the value or good of a flute-player.

Additionally, consider something like Thomas Aquinas's natural law theory. For him, the very nature of things is normative. Certain facts are true of humans by nature: we preserve our lives, we rear our young, we live in societies, and so on (Aquinas 1997, 775). All of these are natural, descriptive facts true of human beings by nature, and yet Aquinas argues that these features are also good for us. Here Aquinas allows - seemingly - a move from natural/descriptive facts to normative ones (about what’s good for humans). Why? It’s plausibly because Aquinas thinks our nature already contains/implies facts about our good (via our end). He claims that “as being is the first thing that falls under the apprehension absolutely, so good is the first thing that falls under the apprehension of practical reason” (774). Practical reason follows from apprehension “absolutely” just as the good follows being. Again, the very nature of things contains within themselves normative properties. Like Aristotle, Aquinas doesn’t divide the natural and normative as sharply as Moore (or, perhaps, even at all).

In these cases, if I’m right, then the movement from a naturalistic claim or property to a normative one won’t be fallacious or defective. That is, given certain meta- physical/ethical/philosophical views that diverge from those of Moore and philosophers like him, there seems to be no inherent or necessary defect in moving from the natural to the normative. Whether the naturalistic fallacy is fallacious, then, hangs upon one’s more substantive philosophical positions regarding metaphysics and metaethics: some of these commitments yield a naturalistic fallacy, and some allow certain natural-to-normative maneuvers.

References

Aquinas, Saint Thomas. 1997. Basic Writings of Saint Thomas Aquinas, edited by Anton C. Pegis. Indianapolis, IN: Hackett.

Aristotle. 2009. The Nichomachean Ethics, translated by David Ross. Oxford: Oxford University Press.

Foot, Philippa. 2001. Natural Goodness. Oxford: Oxford University Press.

Moore, G.E. 1903. Principia Ethica. New York, NY: Macmillan.