Extrinsic and Intrinsic Properties
EXTRINSIC AND INTRINSIC PROPERTIES
An "intrinsic property" is one whose possession by an object at a time involves nothing other than the object (and its parts) at that time; an "extrinsic property" is one whose possession at a time involves something else. We might say, therefore, that the properties of being red and round are intrinsic to this ball, but the properties of being in Rhode Island, being less than five feet away from a tree, and having once been owned by my sister are extrinsic to it.
Peter Geach has made a corresponding distinction among changes. There is change whenever "F(x ) at time t " is true and "F(x ) at time t ′" is false. Socrates will change when he puts on weight; he will also change when he comes to be shorter than Theaetetus merely in virtue of Theaetetus's growth. Changes of the second kind—intuitively less genuine—Geach calls "mere Cambridge changes," without proposing a rigorous criterion. We might define a mere Cambridge property as a property, change in an object's possession of which is a mere Cambridge change. Mere Cambridge properties are plausibly taken to be the same as extrinsic properties.
The matter is important, among other things, for the clear statement of a Humean view of the world. For a Humean there is in principle a description in intrinsic terms of the state of the world at any one time that is both complete and free of implications for the state of the world at any other time. "Solidity, extension, motion; these qualities are all complete in themselves, and never point out any other event which may result from them" (Hume, Enquiry, sec. 8, 1). It is not clear, however, that what Hume says can be true: The motion of an object is hardly free of implications about the state of the world at other times. (If an object at place p is said to be moving at time t, this is standardly in the sense that, at other times more or less near to t, the object is in other places more or less near to p. ) We may have to decide between complete description and a purely intrinsic one.
Two extreme views are that all properties are really intrinsic and that all properties are really extrinsic. Gottfried Wilhelm Leibniz holds the first: "There are no purely extrinsic denominations." His insistence resulted in the drastic denial of the reality of relations and, most notably, of space and time; it has not been widely accepted. A moderate version of the opposite view, that all properties are really extrinsic, might be held by someone, like Karl Popper, who believes that physical properties are essentially dispositional. Both extremes, in different ways, represent a sense that the nature of one thing cannot be divorced from the nature of others. Confidence in a firm distinction between the intrinsic and the extrinsic, on the other hand, is more characteristic of an optimistic Humean.
It is not easy to give a precise characterization of intrinsic properties, and there may not even be a unique idea, so to speak, waiting to be characterized. We might try saying that extrinsic properties are relational properties and intrinsic properties nonrelational. But many intuitively intrinsic properties still in some way involve a relation—squareness involves a relation among the sides of an object. Can we say that intrinsic properties are those that do not involve a relation to anything that is not a part of the object? This is perhaps the clearest criterion, but it may still be incapable of capturing all our intuitions at once. The power to open locks of kind k, for example, apparently involves a relation to external things of a certain kind—which would seem to make it extrinsic. Yet it is a property that a key can have if it is, so to speak, alone in the world—which would seem to make it intrinsic.
It may be helpful to invoke a distinction between relational descriptions of a property and descriptions of a relational property. But that distinction is itself perplexing. Is "possessing what is actually Jane's favorite intrinsic property" a relational description of a first-order property or a description of second-level relational property?
Philosophers have argued in many cases that apparently intrinsic properties are in fact extrinsic. Terms such as old, great, and imperfect, John Locke says, "are not looked on to be either relative or so much as external denominations," but they conceal a tacit relation (Essay ). More worrying are challenges even to the idea that primary qualities, like size and shape, are intrinsic. The size of the ball is, we may think, intrinsic to it. We can describe a scenario where everything else in the universe is twice its actual size while the ball remains the same. But can we properly distinguish this from a scenario where the rest of the world is the same but the ball is half its actual size? Some will argue that length is relational, and the two scenarios make a distinction without a difference: size, after all, is extrinsic. Others will argue instead that even if our descriptions of size are relative, for example, to standard measures, what is described is still an absolute and intrinsic property.
Are any or all of a person's mental properties intrinsic to her? The question is in part about the limitations of methodological solipsism. If Jane could not possess the property of thinking of Bertrand Russell if Russell did not exist, then that property must be extrinsic to her. Some will try to segment referential thought into an internal and an external component; but if that proposal fails, referential thought will typically be extrinsic to the thinker. (Another option is that the thinker, or her mind, extends more widely than her body—and actually includes Russell.) One might argue a similar point with respect to thought about properties as well as about individuals. (A brain that has never been out of a vat does not know what a meter is.) Maybe there are very few mental properties intrinsic to a person; or maybe we should think again about what the notion of the intrinsic is, and what exactly it is supposed to do for us.
Geach, P. T. God and the Soul. London: Routledge and Kegan Paul, 1969.
Leibniz, G. W. "Primary Truths" and "Letters to Des Bosses." In Philosophical Essays, translated by R. Ariew and D. Garber. Indianapolis: Hackett, 1989. See esp. pp. 32, 203.
Lewis, D. K. "Extrinsic Properties." Philosophical Studies 44 (1983): 197–200.
Lewis, D. K. On the Plurality of Worlds. Oxford: Blackwell, 1986. Chaps. 1.5, 4.2.
Locke, J. Essay concerning Human Understanding. Bk. 2, Chaps. 25, 28.
Popper, K. The Logic of Scientific Discovery, 424–425. London: Hutchinson, 1959.
Justin Broackes (1996)