- David Armstrong once said:
There is a certain picture of the physical world that we all cherish in our hearts, although in our philosophical thinking we may consider ourselves forced to abandon it in a greater or lesser degree. According to this picture, the physical world, including our bodies, consists of a single realm of material objects, and perhaps other objects, related in space and enduring and changing in time. Material objects have shape and size, they move or are at rest, they are hot or cold, hard or soft, rough or smooth, heavy or light, they are coloured, they may have a taste, and they may emit sounds or smells. These properties of objects are, on occasion, perceived; but objects continue to have these properties in a perfectly straightforward way when, as is usually the case, the objects, or particular properties of the objects, are not perceived. This is the picture of the physical world to which we are all instinctively drawn (even Berkeley was). We may think that relatively abstruse evidence garnered from scientific investigations forces us to modify this picture. But it is the picture we have gained through perception, and when we are not considering perception as philosophers, we do not think that the evidence of ordinary perception tends to overthrow it in any way.
→ "Armstrong (David) - A Materialist Theory of the Mind", 1968, pp. 239-40
- This intuitive picture of the physical world tells us that there are material objects located in space and time and possessing properties like shape, size, motion or rest (what Locke called the 'primary qualities' and contemporary philosophers call 'intrinsic properties') as well as properties like heat, colour, or smell (what both Locke and many contemporary philosophers call 'secondary qualities'). David Lewis offers a similar picture that adds a tentative commitment to spacetime itself:
We have geometry: a system of external relations of spatiotemporal distance between points. Maybe points of spacetime itself, maybe point-sized bits of matter or aether or fields, maybe both. And at those points we have local qualities: perfectly natural intrinsic properties which need nothing bigger than a point at which to be instantiated.
→ "Lewis (David) - Philosophical Papers Volume II", 1986a, pp. ix-x
- These pictures constitute our way of understanding the physical world, in particular the physical world as it is fundamentally. As Armstrong puts it, these material bodies bearing intrinsic properties and spatial and temporal relations to each other are of what the physical world, including our bodies consists.
- This is no doubt an intuitive picture of the physical world at its most fundamental, a picture we can make sense of, to a large extent can visualize, and one which many of us as metaphysicians indeed do cherish due to our ability to understand it. But is it accurate? Do our best fundamental physical theories confirm this picture? In particular, do our best, fundamental physical theories reveal a physical world consisting of material bodies with intrinsic properties?
- Several philosophers have suggested that the answer to these questions is 'no.' When we consider the picture of fundamental reality given to us by physics, we find only extrinsic properties, relations. We do not find fundamental intrinsic properties. Here is Armstrong again:
[I]f we look at the properties of physical objects that physicists are prepared to allow them, such as mass, electric charge, or momentum, these show a distressing tendency to dissolve into relations that one object has to another. What, then, are the things that have these relations to each other? Must they not have a non-relational nature if they are to sustain relations? But what is this nature? Physics does not tell us. (1968, p. 282)
- In a more recent book, James Ladyman and Don Ross argue for a similar conclusion:
Both [quantum mechanics] and relativity theory teach us that the nature of space, time, and matter raises profound challenges for a metaphysics that describes the world as composed of self-subsistent individuals. In so far as quantum particles and spacetime points are individuals, facts about their identity and diversity are not intrinsic to them but rather are determined by the relational structures into which they enter … [A]ll the properties of fundamental physics seem to be extrinsic to individual objects. (2007, p. 151)
- Such claims then often lead to worries about whether or not a picture of a world fundamentally consisting of relations, with no fundamental intrinsic properties can even be made coherent. Although some philosophers are willing to accept such a conclusion and happily endorse such a metaphysical structuralism (Ladyman and Ross are a clear example; John Hawthorne (2001) also takes the idea seriously), many cling to the intuitive picture. These philosophers reluctantly end up endorsing a kind of Kantian position: material bodies have fundamental intrinsic properties, but since fundamental physical science only reveals the relations these bodies bear to each other, we can never know how things fundamentally are in themselves, what their fundamental intrinsic properties are.
- Our task here will be to evaluate the truth of this claim: that all of the properties of fundamental physics are extrinsic properties. As I will argue, although certainly a lot of what we might have previously thought were cases of intrinsic properties are revealed by physics to be extrinsic, this does not entail that no properties of fundamental physics are intrinsic. Mass, charge, momentum: these may all be extrinsic properties. However, this does not entail the non-existence of fundamental physical properties that are intrinsic. Indeed current, fundamental physical theories do posit intrinsic properties, and in doing so are able to support another picture of fundamental reality that we may cherish.
- We will begin by making more precise the distinction between intrinsic and extrinsic properties that this debate presupposes. The next sections will investigate the status of fundamental intrinsic properties in quantum mechanics1. To make the discussion somewhat manageable and compact, I have put off the question of intrinsic properties in relativity theory and our theories of fundamental interactions to another day, though certainly there are more places to look if one wants to know if there exist fundamental intrinsic properties.
- In this chapter, I have tried to show that despite an interesting argument to the contrary, at least some properties of fundamental physics are intrinsic. And these are indeed the properties that ground the causal powers of material objects in our world.
- Thus, we have no reason at this time to fear that we cannot know the intrinsic natures of things, how they are in themselves.
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