What is the explanatory gap?

David Chalmers, answered from the texts and cited to the page.

David Chalmers answers

The explanatory gap is the gulf between any account of physical and functional processes in the brain and the fact of conscious experience itself. Here is the precise form of the problem. For phenomena like genes, life, and learning, a functional account is a complete account.1 If someone says "you have explained how DNA stores and transmits hereditary information, but you have not explained how it is a gene," they have made a conceptual mistake — being a gene just is performing that storage-and-transmission function.

But if someone says "you have explained how information is discriminated, integrated, and reported, but you have not explained how it is experienced," they have made no such mistake.1 That is a nontrivial further question, and it is the key question in the problem of consciousness. Why doesn't all this information processing go on "in the dark," free of any inner feel?1

A mere account of the functions stays on one side of the gap; the materials for the bridge must be found elsewhere.1 Now, one might worry that this gap is simply a temporary embarrassment — we haven't yet found the right explanatory principles, but we will. Price's suggestion is instructive here: explanatory gaps accompany every causal nexus, and we have simply gotten used to most of them.2

The gap between pressing a remote and the TV turning on is bridged only partially by appeal to electromagnetic principles, since those principles are themselves brute contingent facts about the world.2 If the brain-consciousness gap is analogous, then it too reflects the contingency of the connecting principles — psychophysical laws that could have been otherwise, grounded ultimately at the point where explanation stops.2

What distinguishes the brain-consciousness case from, say, the relationship between biochemistry and life is precisely this: in the biochemical case, the high-level facts are necessitated by the low-level facts, so there is no further contingency in the inter-level bridge and the relationship is transparent to our understanding.3 The brain-consciousness relationship lacks that transparency because the psychophysical bridge is contingent, not constitutive.3

Once we introduce fundamental psychophysical laws into our picture of nature, the explanatory gap is not dissolved but explained — it is only to be expected, given that nature is the way it is.3 The most sophisticated attempt to close the gap without accepting this conclusion is the phenomenal concept strategy, which locates the gap not in the relationship between physical processes and consciousness themselves, but in the relationship between our concepts of each.4

Proponents argue that phenomenal concepts have a special nature that makes an explanatory gap predictable even if physicalism is true, and that this special nature can itself be explained in physical terms.4 If the strategy succeeds, we get a physical explanation of why we find an explanatory gap — which would be the next best thing to a physical explanation of consciousness itself.4

Whether it succeeds is a question I take seriously but remain skeptical about, for reasons the two-dimensional argument against materialism makes precise.

Sources

  1. There is no analogous further question in the explanation of genes or of life or of learning. If someone says, 'I can see that you have explained how DNA stores and transmits hereditary information from one generation to the next, but you have not explained how it is a [gene],' then they are making a conceptual mistake.
    Facing Up to the Problem of Consciousness, p. 8
  2. If Price is right that the explanatory gap between brain and consciousness is analogous, then this suggests that the gap is due to some contingency in the connecting principles, because of underlying brutely contingent fundamental laws. Which of course is just what I suggest.
    Moving Forward on the Problem of Consciousness, pp. 39–40
  3. for other inter-level relationships — that between biochemistry and life, for example, or between statistical mechanics and thermodynamics — there is no explanatory gap analogous to the brain-consciousness gap. The reason is precisely that the high-level facts in these cases are necessitated by the low-level facts.
    Moving Forward on the Problem of Consciousness, p. 40
  4. this view locates the gap in the relationship between our concepts of physical processes and our concepts of consciousness, rather than in the relationship between physical processes and consciousness themselves... they argue that our possession of concepts with this special nature can itself be explained in physical terms.
    Phenomenal Concepts and the Explanatory Gap, p. 305