Why knowledge of physics is unnecessary for doing metaphysics

James Ladyman and Don Ross, in their book Every Thing Must Go (2007), criticize contemporary analytic metaphysicians for not paying enough attention to science, especially physics. They argue that fundamental physics has shown that the whole framework of analytic metaphysics, the kind of atomistic billiard-ball picture of physical reality assumed in common sense, is false, and that analytic metaphysics should be discontinued and replaced with the project of unifying empirical science.

In this post I will not yet discuss their metaphysical (wink wink) interpretation of physics or their idea of "naturalized" metaphysics (which is confused, by the way), I will just point out that they are simply mistaken about the level of ignorance among metaphysicians. Metaphysicians have been aware for a long time of the theories and results of contemporary physics that Ladyman and Ross are referring to. For example, the analytic metaphysician Dean W. Zimmerman wrote this already in 1996:

"Many scientists and philosophers now hold that, if we take contemporary physics seriously, we can only conclude that the traditional concept of extended substance has no application." (Could Extended Objects Be Made Out of Simple Parts? An Argument for "Atomless Gunk")

So if metaphysicians are aware of the empirical inadequacy of the billiard-ball model, why are some of them still using it? The answer is very simple. Metaphysics is about the fundamental nature of reality and goes deeper than mere empirical science. Therefore, empirical science cannot refute metaphysical views that easily. Metaphysics is prior to science, it is a more fundamental type of inquiry, and is thus autonomous from science. Science, on the other hand, is dependent on metaphysics. As I already said in my previous post, metaphysics is necessary for interpreting science (and interpretation is necessary for understanding). Ladyman and Ross cannot simply derive their anti-atomistic conclusions from the bare formalism of physics unless they engage in heavy-duty metaphysics.

Most importantly, metaphysics is about the specifically metaphysical nature of things, and here we slide into the realm of metaphysical possibility. Metaphysics asks: What is causation, metaphysically? What is a law of nature, metaphysically? What is composition, metaphysically? In order to find out the metaphysical nature of, say, causation, it is not enough to look at what causation is in the actual world, i.e. by trying to ontologically reduce the oomph-y, productive notion of causation to conserved quantities. We have to know what causation is in all the metaphysically possible worlds. In one world it could be something, in another it could be something else. Or it could be the same thing in every world by metaphysical necessity. In any case, the only way to understand something metaphysically is to leave the actual world behind.

The same goes for the metaphysical nature of physical objects. It is not enough to know that in the actual world, there are no extended substances. For the purposes of metaphysics it is more important to know whether such substances are possible because such a possibility would have far-reaching consequences, as Zimmerman explains:

"Extended substances are more like gold mountains than round squares. Perhaps there aren't any, but there could be. And if the argument of this paper is correct, the possibility of extended objects implies the possibility of objects consisting of 'atomless gunk'. ... [T]he bare possibility of atomless gunk has far-reaching consequences for the metaphysics of living things and artifacts. ... [I]f there could be objects made of atomless gunk, then ... living things and other objects that can be constituted by different masses of matter at different times must be construed as either (i) a kind of process or event, or (ii) logical constructions out of more basic entities." (ibid; first emphasis mine)

The only way to study bare metaphysical possibilities is to use the traditional a priori methods of metaphysics. Empirical science is, by necessity, silent about these kinds of issues because it aims at mere empirical adequacy, a superficial level of understanding.

When studying the metaphysical nature of objects, one is not obliged to stay in nearby worlds. In fact, the more exotic the worlds, the deeper we get into the very essence of objects. This is why knowledge of physics, which describes only a very thin slice of all the metaphysical possibilities, is unnecessary when doing metaphysics.

Knowledge of physics could even be harmful, because people have the tendency to want to show off their knowledge and do what they have a comparative advantage in. This could lead physics-literate metaphysicians to stay too close to the actual world and provide analyses that are metaphysically shallow. This is often the case with "naturalized" metaphysics.