I think the only interesting positions regarding the metaphysics of qualia are dualisms like Chalmers’, idealisms like Dennnet’s, and identity theories like the Churchlands’. And only the latter two strike me as at all appealing. In this post I’d like to air the following beef with dualism: it constitutes an untenable combination of realism with a lack of empirical depth.
To spell this out, I’ll start by spelling out some terminology, especially what I take the relevant notions of idealism, realism, and empirical depth to be. Let realism about x be the view that x facts outstrip x beliefs and idealism about x to be the view that there is nothing more to x facts than our x beliefs. (Note that in other discussions of realism and idealism what is at stake might be a much broader notion of mind-dependence/independence than the notion of belief-dependnce/independence that I want to focus on here.) By “emprical depth” I mean that property of theories in virtue of which they have the kind of “surplus meaning” that guides scientific discovery and provides predictive and explanatory power.
I suppose that the best reasons for being a realist about anything have to do with the gains in empirical depth thereby achieved. In the physical sciences, being a realist about unobservable particles buys you predictive and explanatory power unavailable to a phenomenalist (a kind of idealist) that construes particle-talk as reducing to statements concerning sets of observations. This is not to say that idealism is always bad. If there were a domain which seemed to lack empirical depth, then we would have good grounds for being idealists about entities in that domain. Here’s a domain that lacks empirical depth: nice shirts. There’s probably not much we can predict or explain about nice shirts. Some shirts are nice, some are not, the end. The science of nice-shirt-ology is not forthcoming. A good position to take on nice shirts then is a kind of idealism: there are no facts about nice shirts (qua nice shirts) that outstrip what we think about nice shirts.
Enough about shirts. What about qualia? Does qualia-talk carry with it any empirical depth? It depends on who you ask. As best as I can tell from dualists, there’s not much empirical depth to be gained from qualia-talk. (Dualists famously maintain that attributing qualia buys you no explanatory or predictive power not had by attributions of zombie-hood.) Identity theorists however, get you empirical depth (for more on this point see “Consciousness, Data, Electricity, and Rock ” ) What I wonder about dualists is this. If qualia-talk lacks empirical depth then what justifies their phenomenal realism? Why not change teams to idealism and buy into something like Dennett’s “first-person operationalism”? Alternately, maybe they could change their mind about qualia-talk and trade shallows for depths.
Figure 1. Pete Mandik dived for empirical depth and Chris Eliasmith took this cool picture of him.
Fig 2. Nice shirt.