Gravity and Consciousness
It is tempting to see an analogy between the mystery of consciousness and the mystery of gravity. Both arose at around the same time (with Descartes and Newton) as the Scientific Revolution was getting underway. Gravity and consciousness seem “occult” to a mechanistic worldview: the brain and the earth are extended objects with mass, while consciousness and gravity are ethereal, invisible, and impalpable. It is natural to imagine them as surrounding these extended objects, like a ghostly penumbra (both are “ghosts in the machine”). Hence a kind of dualism suggests itself: in Cartesian style, we could say that the essence of physical objects is extension and the essence of gravity is attraction, as the essence of the body is extension and the essence of mind is thought. Mimicking Newton, we could assert that consciousness is proportional to the brain’s mass (quantity of neurons) and its amount of electrical activity. There is a mathematical relationship between mind and brain, as there is between the mass of objects and their gravitational force. In both cases this coexists with deep mystery about the nature of the ghostly things in question, and about their manner of dependence (What has mass got to do with attraction? What have neurons got to do with thought?). So, it might be thought that we have the same kind of mystery at work here: it is as if gravity is the earth’s mind and consciousness is the brain’s gravity. Not literally, to be sure, but metaphorically; the two mysteries have the same general structure. They are analogous. We might even liken the way bodies reach out to other bodies and affect their motion by means of gravity to the way that the mind reaches out to distant objects to make them objects of thought. Both involve a kind of targeting or directedness. And isn’t the concept of attraction derived initially from a psychological phenomenon (like the concept of repulsion)?
These points may be granted, but on deeper inspection they emerge as comparatively superficial. Let’s turn to We Have No Idea, particularly chapter 6 (“Why Is Gravity So Different from the Other Forces”). Here Cham and Whiteson explore the mysteries of gravity, asking “Do you really understand gravity?”. They reply as follows: “You see it [gravity] working around you, but when we compare the way it works to the patterns set by the other basic forces, we notice immediately that it doesn’t quite fit. It is weirdly weak, it nearly always attracts rather than repels, and it doesn’t play nice with a quantum view of the world.” (77) As they point out, gravity is extraordinarily weak compared to magnetism (as well as the strong and weak forces): just compare the force exerted by a kitchen magnet to that exerted by the earth—the magnet exerts a stronger force than the earth despite its comparatively tiny mass. Gravity is also peculiar in having only an attractive direction; there is no counterpart to positive and negative charge with attraction and repulsion. Thus, there is no cancelling out of gravitational forces analogous to that which obtains in the case of electromagnetism. Third, the physics of gravity (notably Einstein’s GTR) cannot be unified with quantum theory: there are no “gravitons” playing the role of photons in the physics of electromagnetism. Hence the difficulty of producing a Unified Theory in physics. But none of this applies to the case of consciousness: here we find no parallels to these points about gravity. Nor, I might add, do we find any analogue of the idea that gravity is really the bending of space by massive objects. In fact, consciousness is not a force at all—it is a process or attribute. Consciousness is not a member of a family of other forces like gravity. This is why I say that the analogy is superficial (though not without interest as far as it goes). The mystery of gravity consists in different kinds of considerations from the mystery of consciousness. Gravity is an anomalous force, but consciousness isn’t a force at all and isn’t therefore an anomalous force. The key similarity is that just as Newton couldn’t find the cause of gravitational attraction in matter, so we can’t find the cause of consciousness in the brain (the explanatory cause). There is a gap in our understanding of nature in both cases. But even if there is no deep analogy here, it is still instructive to explore the similarities and dissimilarities between the two cases. It is good to keep a catalogue of the mysteries of nature (to use Hume’s phrase). As Cham and Whiteson observe, “We always need to keep in the back of our minds the larger perspective that we are still in the dark about most of the basic truths about the universe”. (91)