Does Physicalism Leave an Explanatory Gap?

When thinking about certain correlations between our physical body and the mind, for instance c fibres firing and pain, one might come to the conclusion that despite having thorough scientific knowledge about the concept of pain it still not a satisfactory account of how a physical act of c fibres firing gives rise to the conscious sensation of pain. Some philosophers like Levine agree that psycho-physical identity statements leave an inevitable explanatory gap; others like McGinn argue that this gap is potentially closable. Some like Papineau dismiss the problem completely and claim that there is no such thing as an explanatory gap, and all argument around it is purely “slipping back into dualist thinking”(Papineau, 1998)
When we consider psycho-physical identity statements about the mind and body, theoretically they should be analogous to type-identity statements in the external world. For instance when we discover that water is H2O, when presented with evidence, we do not feel inclined to ask why this is the case. However even after ample scientific evidence that pain is in fact c-fibres firing, we would still tend to raise questions as to why pain feels this certain way and not any other way. This impression that despite sufficient physical knowledge the relation is still unexplained is precisely what Levine points out in “Materialism and qualia: the explanatory gap”.
However let us consider what c-fibres firing does in fact explain about pain. Functionalist would argue that the “qualia” of pain have a specific role in our interaction with the environment. For instance stimulation of nerve endings makes c-fibres fire which induces the feeling of pain in order to avoid injury. However emphasis should be made on the difference between why the function exists and how the function works. Certainly the functionalist’s account clarifies the causal role of pain, nonetheless the qualitative aspect of how pain feels remains unexplained. So perhaps with qualia part of the phenomenon cannot be made intelligible and there is no physical explanation of why pain feels the way it does?
It could be true that we merely lack cognitive capacity to bridge the explanatory gap. McGinn suggests that theoretically there could be a priori facts about consciousness in a “hidden dimension” which could be implied from physical facts. But due to our cognitive barriers we cannot possess these concepts and explain mind phenomena. Still the notion is conceivable; meaning that at least in principle the explanatory gap can be bridged.
Moreover it is possible that further scientific progress will assist us in spanning the gap. Arguably it is conceivable but contra - intuitional to incorporate the non-spatial character of consciousness into the physical realm. Nonetheless scientific history shows that a lot of physical concepts taken for granted today seemed unintuitive at first. The incorporation of the mental in the physical would solve problems with description and thus a direct connection between what a mental state is like and its purely physical causes could be established.
But, according to Levin, even if the problem of psycho-physical identity statements is solved, the metaphysical conclusion that qualia are physical still presents an explanatory problem.
Papineau sees no such problem and claims the intuition for the explanatory gap merely exists because physicalism seems so implausible to most people. “It’s not that mind-brain identities are hard to explain—they are simply hard to believe.”(Papineau, 2008). H2O does not cause water, water is H2O. In the same way c-fibres firing does not cause pain, it is pain. It is an identity just like water=H2O and does not need further explanation. Further he argues that despite there being compelling arguments in favour of physicalism, it is in human intuition to think that mental states are something more than merely physical brain processes. However this intuition does not mean there is in fact something non-physical to mental processes and that brain processes cannot be explained by physical facts. Nonetheless when someone asks why the colourless, odourless liquid is H2O we can refer to the physical and chemical makeup of water and explain these properties. Shouldn’t we be able to do the same with c-fibres firing and the sensation of pain? i.e. explain why certain descriptions satisfy the definition of pain. Papineau argues that the water=H2O model is an unreliable analogy for psycho-physical identities. In the case of water we can show that certain physical properties in fact satisfy some a priori descriptions associated with water. This then can be used to draw the conclusion that water is H20. In contrast, there no such a priori properties associated with mental states, so the same line of argument is not applicable. “This pattern of argument is fine when our pre-theoretic concepts are associated a priori with functional descriptions, but there is no need to insist on this form of identification when our concepts are not”.(Papineau, 1998)
Hence with psycho-physical identities there is nothing to explain in metaphysical terms. The fact speaks for itself, and there is nothing beyond it we can acquire. The reason we think that an explanation is still intelligible demonstrates “we still conceive of the relata in the identity claim as distinct properties, or, perhaps, the one thing as manifesting distinct properties.”(Levine, 2009) We are unable to accept that a mental property is the same as its physical associate. This inability is merely a product of human psychology, but it does not mean that this intuition in fact indicates some truth.
In conclusion the notion of an explanatory gap is intuitive to human beings and is hard to reject. Perhaps humans are too stubborn to reject an intuitive notion. Perhaps we don’t have the mental capacity to grasp concepts that would explain the gap, or maybe we don’t have enough memory and time capacity to think of a solution and possibly in future a solution could be developed. However from the current stand of human progress the gap seems very wide and impossible to span.

Chalmers, D. 2007 “Phenomenal Concepts and the Explanatory Gap”
Chalmers, D. 1997 “Moving forward on the Problem of Consciousness”
Levine, J. 1983. “Materialism and qualia: the explanatory gap”.
Levine, J. 2009 “Conceivability, Identity and the Explanatory Gap”
Papineau, D. 2008. “Kripke’s Proof That We Are All Intuitive Dualists”
Papineau, D. 1998 “Mind the Gap”