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It seems currently almost compulsory to begin a neuroscientific lecture on the nature of conscious experience with a comment about how wrong Descartes was. Despite this, as Daniel Dennett has commented, if the lecturer goes on to describe a model explicit enough to include a flow diagram it tends to include precisely the sort of 'place where the contents of experience come together' that Descartes argued must exist. This seems hardly surprising, since if signals encoding the contents of experience are not brought together, or integrated in some sense, it is hard to see how the brain can respond to the total pattern they constitute - a familiar face for instance.
In my view it is unwise to dismiss Descartes too quickly. Most attempts to do so confuse a number of different aspects of his account, some of which he seems to have got wrong but others he almost certainly got right.
Dennett claims (in Consciousness Explained pp106-111) that there are no 'inner observers' in brains. However, his supporting arguments are hard to follow. He objects that 'if the point of view of the observer must be smeared over a rather large volume of the observer's brain…' then there is no fact of the matter about whether signal A comes before signal B or vice versa, since there will be time lags within the brain. Time lags in the brain may be relevant but the argument seems back to front since Dennett claims to be arguing against a model in which the viewpoint is not smeared all over the brain, but in one tiny part of it. The rest of his argument appears to rest on a vague analogy with tax revenues! Dennett claims to be a hard core physicalist yet seems to abandon the most basic requirements for a model consistent with the causal chains of physics.
As I see it the central problem here is a confusion between two quite different proposals. The first, which is that of Descartes, is that there is one place in a brain where all the contents of experience come together. I agree with Dennett that this is a bad idea, but for rather different reasons. The second proposal is that there are one or more places in a brain where all the contents of experience come together, with the likelihood that there are many. Dennett's own model involves multiple sites where contents of experience are available. The strange thing is that rather than saying these are sites of experience he suggests they are just sites of 'drafts', leaving unclear how such drafts help to explain experience. Why not just say that there are lots of sites of experience?
Dennett refers to the intuition of a unity of consciousness, which might seem at odds with there being many experiences at the same time. However, this suggests a further confusion: between two meanings of unity. One meaning is that all the elements of an experience seem to be available together. The second meaning is that there is only one instance of their being together. The first of these seems to make sense computationally, quite apart from being hard to deny in a subjective sense. The second has no rational basis or subjective support. If there are lots of experiences at the same time in a brain there is no reason to think they would include information about each other's existence since our brains are not primarily set up to tell us about their own structure. Moreover, the idea of experiencing other experiences runs contrary to everything we know about experience - it is hard to see what it could mean.
(There are complex issues around what might actually be meant by signals encoding content coming together. In a parallel system like a brain a single signal can encode a vastly complex pattern. The arguments are simplified but it remains the case that without any inner receiving units doing the experiencing any account of experience is divorced from a local causal pathway and is thus the very opposite of 'materialist'.)
