In this chapter I will try and illustrate what I mean by an explanatory gap, and why I believe there has to be one.
When studying sciences, there’s a lot of different statements we can make about the world, physical statements like these can for example be:
Pain is the firing of C-fibres
Heat is the motion of molecules
Let us suppose both of these statements are necessarily true. They are true in a sense that it is not possible in whatever world for these statements to be false. And now let us imagine a world in which it is possible to have heat without the motion of molecules, or pain without the firing of C-fibres.
There is a notable difference between these two statements, in the sense that statement 1 is a physical-mental statement, whereas statement 2 is purely theoretical. When we imagine heat without the motion of molecules, it is still fully explanatory in other terms. And in general, we can explain everything about statement 2, without leaving anything important out. Once we know the causal role of heat, we basically can say anything about it using the laws of chemistry.
But when we try to explain pain without the firing of C-fibres there is a problem that arises: we cannot explain just the experience or sensation of pain without this physical process. It seems impossible because all we are left with is the sensation or experience of pain, which does not seem explanatory in physical terms at all. We are incapable of explaining pain in terms of physics, chemistry, biology or any other science, when we leave out the firing of C-fibres. It is true that pain is partially explanatory in physical terms, but the mental, what-it-is-like to feel pain aspect, seems to be left out. Our consciousness seems to play an important role in this problem.
Consciousness makes the mind-body problem complicated. Consciousness is that what it is like to have a certain experience. It is that what it’s like for a person to see something blue, hear music and so on. In each of these cases, I am the subject of a mental state with a very subjective character. There is something it is like for me to undergo each state. We are usually conscious when we are awake or when we are dreaming. Each conscious state is a way of being conscious. Philosophers often use the term ‘qualia’ to refer to the subjective qualities of our conscious experiences. The main problem with qualia is the difficulty of explaining them in terms of sciences or physical phenomena. We cannot explain consciousness in the way we can explain a mathematical formula, a chemical reaction or biological phenomena. Even if I could have perfect knowledge of all physical facts in our universe, I would still have difficulties explaining to others the hurtfulness of pains, the itchiness of itches, or the characteristic experience you have when tasting food. Qualia seem impossible to explain to others. The explanatory gap is this gap between the physical, explanatory things, and our non-physical, mental, non-explanatory states.
2. The “Point of view” of someone’s conscious states
Another example that shows that there must be an explanatory gap between the mental and the physical is the fact that we are unable to understand another person’s or organism’s state of mind.
According to Thomas Nagel, an organism can only have consciousness if there is something it is like to be that organism. The organism must have some sort of conscious states that involve qualia. And here is where again we encounter the ‘gap’ between the mental and physical. We can have all knowledge of neuroscience and biology, and in that way get to know everything about another organism or human being, but can we ever find out what it is like for, for example my sister Julie, to be Julie? It seems that even if we had perfect knowledge of Julie as a human being, and knew all the facts about her brain states and biological build, we can never have the right model to explain her conscious states. Julie’s personal experience of qualia seems inaccessible to us. We cannot explain her mental states using physical or objective terms like we can use reduction to explain A in terms of B when comparing two physical phenomena.
It seems that Julie experiences everything from her personal point of view, which only she has access to. It is difficult to understand the objective character of an experience apart from our own. Without a point of view, we are leaving something crucial aside. The reason why we can never sufficiently provide an explanation for our conscious states is also our incapability of seeing things objectively. Our point of view is always a part of us we cannot let go of.
It is true that we can try to take up a point of view to understand somebody else, but we can only do this in physical terms : we can know what the quality of another person’s experience is, knowing that Julie feels pain, but we cannot know what it is like for the other person to have that experience. We can then explain pain in terms of the physical again, but something we automatically will do is refer to the phenomenon pain as the experience we have ourselves when we have pain. It seems impossible to escape our point of view. Therefore even objectivity is impossible when talking about the mental or consciousness.
3. The possibility of inverted qualia
Another example that shows there is an explanatory gap, is the experiment of inverted qualia.
There is a theory in philosophy that states there is a possibility that different human beings experience certain qualia, like colors for example, in a completely different way than others. They see in fact the opposite side of the color spectrum, without knowing this.
For example, Julie perceives colors in the exact opposite way that I do. So if I am looking at ripe tomatoes and experience the visual quality normally associated with ripe tomatoes, my inverted sister Julie will experience the quality normally associated with a cucumber. We do however both refer to the tomatoes as red, since we have both learned from birth that tomatoes are red. We still refer to a certain color in the same way as others do, because we are taught to call certain colors certain names from the moment we are born. And we can never know if somebody else experiences qualia the same way as I do.
How could I explain to Julie what conscious experience I have when seeing the color red? This seems impossible, simply because we lack the terms that we can use when describing the physical phenomena of color. And so we can never compare our different experiences of color, the other person’s consciousness remains a mystery to us.
We can give sufficient physical explanations of color, explaining different wave-lengths of light, reflections and so on, but it seems that there is again a gap between the physical aspects of color, and the explanation of our experience of color.
Conclusion
In the light of what has been discussed in this essay; I believe we must conclude there is an explanatory gap between the mental and the physical. This is because we currently have insufficient terms, and no physical model to explain our mental states. I believe however that in the future it is completely possible that if we advance in science, we might find a new way of giving explanations concerning the mental. But at the moment, the mental and the physical seem completely distinct.
Levine, J., 1983, “Materialism and Qualia: The Explanatory Gap”, Pacific Philosophical Quarterly, 64, 354-61
Michael Tye, Stanford encyclopedia of Philosophy, Qualia
Jackson, F. Epiphenomenal Qualia. Philosophical Quarterly 32: 127-136
Nagel, 1974, T. What is it like to be a bat?
Byrne, A., 2001, “Intentionalism Defended”, Philosophical Review
Levine, J., 1983, “Materialism and Qualia: The Explanatory Gap”, Pacific Philosophical Quarterly, 64, 354-61
Nagel, T., 1947, ‘What is it like to be a bat’?