On reductionism

All the talk on reductionism as of late has kept my mind quite occupied. So occupied, in fact, that I felt the need to devote an entire post to reductionism itself. Though reductionism does come in different forms, this post will deal with the form that claims that an object is nothing but the structure of its physical constituents. This form of reductionism is very appealing to naturalists for the following reason. If the natural world is all that exists, then objects are nothing but physical particles in different structural forms. Hence, a lump of bronze and a bronze statue consist of the same matter simply arranged differently.

The initial difficulty with this view was articulated perfectly by attentive commenter JD Walters:

[D]escribing a cat as a mere 'amalgam of physical properties' is the (metaphysical) bundle theory of particulars and has all sorts of problems, including the consequence that if even one of the cat's properties changed, even the number of hairs on its body, we would be dealing with a different cat.

Let us expound JD’s argument here. Let’s take a cat, which on reductionism is nothing but a hunk of matter arranged cat-wise. This cat, then, is defined by the structure and arrangement that the particles are exhibiting. So, now let us remove a single hair from its body. What do we now have? Well we now have a cat with a different physical arrangement than before, and thus we have a different cat altogether. Why? Because cat A (the first cat), though it looks the same as cat B (the second cat), has more physical constituents than cat B—the difference between their constituents being the particles that make up a hair—and thus has a different physical arrangement than B. Hence, since cat A’s matter has a different structure and arrangement than cat B’s matter, then cat A and cat B are not the same cat, on reductionism.

Now, this certainly seems to run counter to our common sense—though the fact that it runs counter to common sense only demonstrates that reductionism, then, runs counter to common sense. For when a cat goes for a haircut, say, we don’t really believe that the post-haircut cat is a different cat than the pre-haircut cat. But, this only means that there must be something more to a cat than its mere physical constituents.

However, one attempted rebuttal that I’ve heard so far from reductionists is that the reason we still consider cat A the same as cat B is because our brains still categorize that there are defining characteristics or properties in cat B that make it the same as cat A. But this response runs into problems. First, how our brains characterize objects is superfluous to the discussion at hand. Talk about how our brains characterize objects is epistemological, as well as psychological, while talk of what actually makes an object an object in mind-independent reality is ontological. Hence the above objection is only conflating ontology with epistemology. To reiterate, when we talk of reductionism we’re talking about what makes an object that very object—i.e., what makes a cat a cat, as opposed to a frog. Thus stated, we’re interested in substances in themselves, and not how we perceive or categorize those substances.

Second, this objection, even if we ignore its metaphysical conflation, still does absolutely nothing to answer the original point. Remember that on reductionism an object is nothing but the arrangement or structure of its physical constituents. So if cat A has a different structure (even by a few particles) than Cat B, then, on reductionism, they cannot possibly be the same object. And thus it makes no difference whatsoever how we categorize said objects, because they are necessarily different objects because they have different physical constituents and structures!

Furthermore, the topic of how we categorize objects, based on an ontology of reductionism, leads to further absurdities in itself. Let us return to cat A and cat B. It is true that the difference (a hair) between A and B is miniscule when we perceive it, and therefore our visual perceptions will regard A and B as the same. But what if the difference is greater? What if cat B is also missing a leg? Can cat B be recognized as cat A? Well, not in the way the reductionist would want, since, again, cat B has different (less) physical constituents than cat A, and such constituents have a radically different arrangement than cat A as well. But suppose, contra the conclusions of reductionism, that the reductionist still wants to affirm B and A to be the same cat. Well, we can go even further. Suppose cat B is missing a tail, an eye, and an ear, in addition to its missing leg. Suppose the cat continues to deteriorate. At exactly what point is this cat B, on reductionism, no longer cat A? Notice here that the reductionist would be stuck in a dilemma, because at whatever point he identifies that the physical arrangement of cat B no longer constitutes cat A, the only argument for stopping at that specific point, consistent with reductionism, can be that cat B’s arrangement or structure is different from cat A’s—because, again,  on reductionism an object is defined as nothing but its physical constituents. Now if the reductionist wants to claim instead that cat B is different than cat A because it no longer retains the properties that make it cat-like, then the reductionist has given up reductionism. For admitting that there are properties inherent in a substance or object that make it that very substance is to give up reductionism. That is, it is to admit that there is something in a substance over and above its physical structure that makes it a certain substance.  

But we can push even further against reductionism, by returning to our original difference (one hair) between cat A and cat B. Notice that if cat B has the same structure as cat A minus one hair then cat B’s structure and arrangement is subsumed under the structure and arrangement of cat A. That is to say, cat A’s arrangement contains the arrangement of cat B. Now we can continue this process by removing two, three, and four hairs etc., to create a cat C, D, and E etc. Notice that each subsequent cat is contained in the former ones. That is to say, cat A contains all of cat B, C, D, and E etc. But this leads to something quite peculiar. Since, on reductionism, all of these cats have different structures and arrangements then they are all different cats. But this means that cat A literally contains cat B, C, D and E etc., which means that present in cat A is a multitude of other different cats at the same time in the same place! Such is the absurdity of reductionism.

Reductionism, then, turns out to not only go against common sense but, also, to lead to absurdity. Obviously, then, an object or substance cannot be nothing but its physical constituents. Thus stated, there must be something more to substances in themselves over and above their parts.