Kristjan Loorits says he has a solution to the Hard Problem, and it’s all about structure.

His framing of the problem is that it’s about the incompatibility of three plausible theses:

1. all the objects of physics and other natural sciences can be fully analyzed in terms of structure and relations, or simply, in structural terms.
2. consciousness is (or has) something over and above its structure and relations.
3. the existence and nature of consciousness can be explained in terms of natural sciences.

At first sight it may look a bit odd to make structure so central. In effect Loorits claims that the distinguishing character of entities within science is structure, while qualia are monadic – single, unanalysable, unconnected. He says that he cannot think of anything within physics that lacks structure in this way – and if anyone could come up with such a thing it would surely be regarded as another item in the peculiar world of qualia rather than something within ordinary physics.

Loorits approach has the merit of keeping things at the most general level possible, so that it works for any future perfected science as well as the unfinished version we know at the moment. I’m not sure he is right to see qualia as necessarily monadic, though. One of th best known arguments for the existence of qualia is the inverted spectrum. If all the colours were swapped for their opposites within one person’s brain – green for red, and so on – how could we ever tell? The swappee would still refer to the sky as blue, in spite of experiencing what the rest of us would call orange. Yet we cannot – can we? – say that there is no difference between the experience of blue and the experience of orange.

Now when people make that argument, going right back to Locke, they normally chose inversion because that preserves all the relationships between colours.  Adding or subtracting colours produce results which are inverted for the swappee, but consistently. There is a feeling that the argument would not work if we merely took out cerulean from the spectrum and put in puce instead, because then the spectrum would look odd to the swappee.  We most certainly could not remove the quale of green and replace it with the quale of cherry flavour or the quale of distant trumpets; such substitutions would be obvious and worrying (or so people seem to think). If that’s all true then it seems qualia do have structural relationships: they sort of borrow those of their objective counterparts.  Quite how or why that should be is an interesting issue in itself, but at any rate it looks doubtful whether we can safely claim that qualia are monadic.

Nevertheless, I think Loorits’ set-up is basically reasonable: in a way he is echoing the view that mental content lacks physical location and extension, an opinion that goes back to Descartes and was more recently presented in a slightly different form by McGinn.

For his actual theory he rests on the views of Crick and Koch, though he is not necessarily committed to them. The mysterious privacy of qualia, in his view, amounts to our having information about our mental states which we cannot communicate. When we see a red rose, the experience is constituted by the activity of a bunch of neurons. But in addition, a lot of other connected neurons raise their level of activity: not enough to pass the threshold for entering into consciousness, but enough to have some effect. It is this penumbra of subliminal neural activity that constitutes the inexpressible qualia. Since this activity is below the level of consciousness it cannot be reported and has no explicit causal effects on our behaviour; but it can affect our attitudes and emotions in less visible ways.

It therefore turns out that qualia re indeed not monadic after all; they do have structure and relations, just not ones that are visible to us.

Interestingly, Loorits goes on to propose an empirical test. He mentions an example quoted by Dennett: a chord on the guitar sound like a single thing, but when we hear the three notes played separately first, we become able to ‘hear’ them separately within the chord. On Loorits’ view, part of what happens here is that hearing the notes separately boosts some of the neuronal activity which was originally subliminal so that we become aware of it: when we go back to the chord we’re now aware of a little more information about why it sounds as it does, and the qualic mystery of the original chord is actually slightly diminished.

Couldn’t there be a future machine that elucidated qualia in this way but more effectively, asks Loorits?  Such a machine would scan our brain while we were looking at the rose and note the groups of neurons whose activity increased only to subliminal levels. Then it could directly stimulate each of these areas to tip them over the limit into consciousness. For us the invisible experiences that made up our red quale would be played back into our consciousness, and when we had been through them we should finally understand why the red quale was what it was: we should know what seeing red was like and be able for the first time to describe it effectively.

Fascinating idea, but I can’t imagine what it would be like; and there’s the rub, perhaps. I think a true qualophile would say, yes, all very well, but once we’ve got your complete understanding of the red experience, there’s still going to be something over and above it all; the qualia will still somehow escape.

The truth is that Loorits’ theory is not really an explanation of qualia: it’s a sceptical explanation of why we think we have qualia. This becomes clear, if it wasn’t already, when he reviews the philosophical arguments: he doesn’t, for example, think philosophical zombies, people exactly like us but without qualia, are actually possible.

That is a perfectly respectable point of view, with a great deal to be said for it. If we are sceptics,  Loorits’ theory provides an exceptionally clear and sensible underpinning for our disbelief; it might even turn out to be testable. But I don’t think it will end the argument.