The Observer has a discussion between Tallis and Eagleman, Eagleman representing neural reductionism and Tallis speaking for a more traditional view of mind and brain.

Although it’s worth reading, it turns out a slightly inconclusive encounter. Perhaps on this occasion you’d give Tallis a points victory because he does seem to be looking for a fight, whereas Eagleman is in rather cautious form. They circle each other but never quite identify a proposition which sums up their disagreement clearly enough to get things going.

What seems to emerge is a kind of agreement that mental activity needs to be addressed on more than one level of explanation, with the two antagonists merely giving a different balance of emphasis. This certainly understates the real disagreement between the two.

I think it probably is the case that nearly everyone grants the need for more than one level of explanation. There are those who would say the correct top level is the cosmos itself and that individual consciousness expresses a universal entity.  Not quite as high-level as that we surely need to address consciousness on the level of its explicit and social content; we could call this the ‘home’ level because it is sort of where we live, where we actually experience the world. Most would agree that there are levels of unconscious operation that are also a necessary part of the picture; not many people would say that the structure of the brain and its component neurons tell us nothing; and a majority nowadays would agree that there is ultimately a story at the classical molecular level which, though vastly complex, cannot  be ignored. Some say even this is not enough and that consciousness cannot be understood without giving quantum mechanics, or some as-yet-unknown lower level theory, a crucial role.

Only a very hard-line reductionist would say we only need one of these levels: it’s generally accepted that there are interesting things to be said on several of them which simply cannot be addressed at other levels. What mainly emerges here is Tallis’ defence of the ‘home’ level against Eagleman’s contention that we pay it too much attention and that for many purposes, including our treatment of crime and punishment, we should dethrone it. Intuitively, the motives for Tallis’ incredulity are pretty clear: wouldn’t it be weird if we had developed the apparatus of thought and consciousness and yet it had no important impact on our behaviour? Don’t we just know that discussion and conscious thought ultimately shape what we do, even if our behaviour is sometimes nudged in different directions by factors we’re not aware of?

Yet there is something deeply unsatisfactory about the whole idea of different levels of explanation, isn’t there? How can one reality require half-a-dozen different accounts? It seems a distressingly messy and arbitrary kind of way for the world to be set up, and certainly we greet any successful reduction of higher level entities to lower level ones as a valuable explanatory achievement. So it’s not hard to sympathise with Eagleman’s desire to emphasise the role of levels below consciousness either.

Generally speaking it seems that the lower the level of our explanation the better, as though ultimate reality resides at the lowest micro level we can get to. We always celebrate reductions, not elaborations. Yet there have been some rebellious attempts to push things the other way through ideas such as emergence and embodiment, which claim the whole can be more important than the parts. I notice myself that things seem to come most clearly into focus at or slightly below the home level: if we go far above or below that we start to get into regions where we have to deal in probabilities or slightly fuzzy concepts. Most notably there don’t seem to be identities at other levels in quite the sharp way there are on the home level. Even molecules are interchangeable: they tell us that it’s almost certain we’re breathing at least one atom from the oxygen previously breathed by Julius Caesar, but how could you possibly tell? You can’t label an atom. Another one of the same kind is distinguishable only by where it is. When we go further down even spatial positions start to get a bit smudged. Equally if we start going up the chain we can only draw slightly fuzzy conclusions about what my family, or the society I live in, thinks or does. This might be a reason to think that real reality is around the home level – or it might a reason to think that the whole business of levels simply flows from my restricted viewpoint and limited understanding.

Perhaps, if my brain were capable of holding it, there is a view on which all the levels could come together. After all, I go on thinking about temperature even though I know it is only molecular motion: perhaps in the end we’ll find a way of thinking about the different aspects of mental activity which brings them together without eliminating anything. Perhaps then it might become clear that Eagleman and Tallis don’t really disagree at all. I wouldn’t put any money on that, though.