Mental Ontology and the Identity Theory

Mental Ontology and the Identity Theory

The identity theory, type or token, has always sounded funny—that was its charm, its novelty. It wasn’t that we had discovered the identity by ordinary scientific means; it was a philosopher’s conceit, an audacious hypothesis. Neurophysiologists never talked this way; they limited themselves to assertions of correlation (vague, non-committal). It wasn’t like Hesperus and Phosphorus or water and H2O. But why does it sound funny—a kind of logical solecism or category mistake? Because it doesn’t come with an individuating sortal concept or different modes of perceptual presentation. “Pain is identical to C-fiber firing” is not a normal identity statement like “Hesperus is identical to Phosphorus” or “Superman is identical to Clark Kent”. It is a kind of pseudo identity statement: where is the sortal, and by what observations did we discover it to be true? We are being asked to accept it on faith as what it appears to be. It is certainly not like a regular identity statement about physical substances such as planets, mountains, animal bodies, atoms. We didn’t trace pain through space and find that it met up with C-fiber firing in a single entity. It is just stipulated that the two are identical.

The fact is that the concept of identity requires a suitable ontology—roughly, an ontology of objects. Not just any old thing lends itself to well-formed identity statements: fictional entities, logical connectives, facts. Identity statements about these things sound funny, contrived, empty. We can’t discover that Hamlet is identical to some other fictional character—say, Macbeth; there is no path from Hamlet to Macbeth through space and time. Gods don’t divide neatly into the identical and the distinct—they have the wrong ontology (being non-existent). And when did anyone think it worth saying that logical conjunction is identical to such-and-such? That could be at best analytic, unlike the psychophysical case. Nor are facts clearly divided into the identical and the distinct, notoriously so; it sounds peculiar to say that the fact that London is the capital of England is identical to the fact that the largest city in England is the capital of that country, because facts are not well-individuated objects. It’s like asking whether sakes are identical with other sakes or other things entirely—sakes are not objects in good standing. Not everything you can talk about is subject to meaningful (and true) identity statements. In fact, it is completely unclear whether events in general are susceptible to identity claims—they don’t allow of the usual methods of identity verification. People never cite events as paradigm cases of true a posterioriidentity statements: putative examples are contrived and no workable criterion of identity suggests itself. The identity relation is quite particular about what it will happily relate. You can’t just stick the identity sign between two words and hope for the best.

Suppose a zealous identity theorist were to claim that irascibility, likeability, and funniness are identical to states of the nervous system. A logical behaviorist will protest that this is a category mistake—a logical howler—because such words are correctly analyzed as hypotheticals about behavior. If the behaviorist is right about that, then the identity theorist is trading in nonsense—his theory is logically ill-formed. The identity theorist misunderstands the logic of mental language. Or suppose an ambitious identity theorist were to claim that materialism about ethics is true because good acts are identical to brain states: to act virtuously is for the V-fibers to fire. That sounds like a bonkers theory of ethics (“central state ethical materialism”). Acting virtuously is not the kind of thing that can be reducible to (identical with) a physical state of the nervous system. Similarly, sensations and beliefs are logically not the kinds of things that could be identical to a brain state, because they are not spatially individuated, possess mass, and have shape. It is no use insisting that they are these things if the identity theory is true; the question is whether that theory is true, or even well-formed. On the face of it, it is not; these are pseudo identity statements conjured up from mere correlations. They sure as hell seem like pie-in-the-sky, i.e., linguistic monsters. Is reasoning validly reducible to a brain state with which it is identical? Hardly, because validity is a normative notion. No doubt there is something going on in your brain when you reason validly, but that isn’t to say the latter is identical to the former, i.e., nothing more than that. When you speak of mind you don’t refer to objects in the brain.

What is going on here? I think the answer is obvious: the ontology of mind is not cut out for psychophysical identity statements. There are no mental substances or even mental events in substances. These are fictions created to squeeze the mind into manageable parcels. The substance ontology is perfect for the perceptible material world, but not for the world of the mind.[1] And it’s not that we have an alternative ontology of mind—we have no articulated ontology, just impressions and vague feelings. We can’t really conceptualize the mind beyond primitive categories (think of worms trying to represent the physical world to themselves). In particular, the familiar spatial scheme fails to apply to the mental landscape (see what I just did?). There are no mental objects (substances) to be identified with physical objects; the logical behaviorist was right on that point. Mental ontology is beyond us save for inchoate intimations: we don’t really know what belief is, or desire or sensation or intention. The identity theorist tries to impose an ontology on the mind by main force, modeling it on the body, but he thereby falls into category mistakes and logical chimeras. Correlations cannot be hardened into identities; pain is correlated with C-fiber firing, but it isn’t identical to it. This is why we can’t say “pain is the same F as C-fiber firing” for some sortal count noun F. Not all ontologies are alike.[2]

[1] See my “Ontology of Mind” and “Mental Ontology”.

[2] The thesis of this paper will be hard to swallow for anyone steeped from student days in the literature of the identity theory, with its casual talk of mental states, mental events, and mental processes—the apparatus of physical discourse without the substance (so to speak). It is difficult not to think in this way, though Wittgenstein and Ryle (among others) tried to discourage it, falling into behaviorism instead. I am recommending agnostic anti-substantialism. We don’t know what mind is such that it could be subject to an identity theory. Tautologically, pain is identical to pain, but that’s about as far as we can go. No doubt, pain is bound up with the brain, but that degree of materialism is a far cry from a reductive identity theory. It may even be supervenient, but supervenience is not identity.