Atoms, Gunk, and God: Natural Theology and the Debate over the Fundamental Composition of Matter

LET US SAY we take a rock and divide it in two. We then divide each of the halves again. We repeat. We keep repeating, over and over and over again, until we have reached down to the level of molecules and then to atoms and then to subatomic particles and beyond. What, eventually, will we end up with? (A) Do we eventually reach “rock bottom,” a layer of fundamental objects that can be divided no further? Or (B) could the dividing process be carried on forever?

Let us take (A), the idea that there are fundamental, indivisible objects. We may call these “atoms,” and the theory that affirms their existence atomism. (I use the label for historical reasons; the “atoms” discussed in the history of metaphysics are of course not equivalent to the atoms of contemporary physics, which are divisible into constituent subatomic particles.) What must be the nature of these objects? Here we can identify two distinct versions of atomism.

According to the first, these entities cannot be spatially extended, since extension entails divisibility. After all, if something has discernible length, then its conceptually distinguishable left and right halves, for instance, could be separated from each other, at least in theory. The existence of the matter constituting the left half seems not to entail the existence of the matter constituting the right half or vice versa, so one could persist without the other (e.g., the left half could be annihilated while the right half continues in existence), and could be divided from the other. Whether they could actually be separated by us, using current or future technology, is of course an entirely different question from the philosophically significant issue of divisibility in principle. Atoms are, on this view, extensionless “point particles” with no actual or potential proper parts. This may be called atomism version 1.

According to the second version of atomism, these indivisible objects are nevertheless spatially extended. The reality of atoms is affirmed, but the relation obtaining between extension and divisibility, which is supposedly entailed, is rejected. Despite being spatially extended, these particles cannot possibly be divided. Consequently, although they are spatially extended, they do not possess actual proper parts in the sense that “proper part” is typically understood (i.e., as involving smaller constituent objects, which could in theory exist apart from the whole). The claim is not merely that they cannot be divided by us using current or future technology, nor that their division would be inconsistent with contingent physical laws. The impossibility referenced here is not mere physical impossibility. Rather, the claim is that it is metaphysically impossible (and logically impossible, for those who equate metaphysical and logical impossibility) for them to be divided. There is no possible world in which these entities are in any way divided, either by splitting in two or by destroying one section while leaving the rest intact. This may be called atomism version 2.

Atomism’s major competitors may be grouped under the affirmation of (B), according to which division could go on forever. Matter is infinitely divisible. But what does infinite divisibility imply? Here there is a further divergence of views. One camp affirms the gunky view of matter. On this view, a material object is infinitely divisible because it is composed of an actual infinity of proper parts: any material object is composed of smaller proper parts that are themselves real objects composed of smaller proper parts that are themselves real objects composed of smaller proper parts, and so on, ad infinitum. Another camp denies the reality of actual infinities (at least in the material realm), and affirms instead the reality of extended simples. On this view matter is infinitely divisible, as on the gunky view, but not because material objects are composed of an actual infinity of smaller objects. Instead, material nature bottoms out (in a sense) at objects that are spatially extended and potentially subject to division, but that lack actual proper parts. They are not composed of real, smaller objects. Rather, what makes it true that the object...