The claim that there is something (the quality of phenomenal experience) that cannot be explained by physical science is strictly analogous to the 19th century “vitalist” claim that the property of being alive could not be explained by physical science (the phrase “élan vital” was actually coined later, in 1907, by Henri Bergson in his book Creative Evolution). Consider all of the physical facts about physical states and processes in the body, the vitalist argued: singularly or together none of these facts entail that the body be alive.
This “hard problem” was never “solved.” It simply faded away as organic chemistry and physiology steadily explicated the physical mechanisms and processes occurring in various parts of cells, and in the various organs of the body. This took some time, well into the 20th century, but by the 1940s, anyway, it was no longer credible to claim that “life” was something that might not be present when these mechanisms and processes of organic chemistry were present, or might be present in their absence. “Life” will always be an ambiguous concept to some extent (there is ongoing debate as to whether viruses are living, for example), because it is an emergent property, but its physical nature is no longer seriously challenged. The concept of “consciousness” is now undergoing the same evolutionary process – not a similar process, the very same process.
This analogy has been prominently rehearsed by Patricia Churchland and by John Searle, among others. I will consider Searle’s version a little more closely by way of setting up the last chapter, where I will discuss the relationship between intentionality and consciousness. Searle makes an analogy between the solidity of a table and the consciousness of a brain: the table’s solidity is a macro-property that emerges from the micro-properties of the wood molecules (which are lattice-like). Consciousness, he suggests, is a macro-property that emerges from the micro-properties of neurons (although he doesn’t claim to know which micro-properties or why).
There are two problems with Searle’s analogy. First, in the case of the wood molecule and the table, they share the same property in the first place: the lattice-like structure of the wood molecule, like a folded piece of paper, just is solid (can bear weight by virtue of its structure). So solidity is not an “emergent macro-property,” solidity is already a property of the “micro” ingredients. If the question is “How can physical objects support weight?” then appeal to the weight-bearing nature of the wood molecule only pushes this question back a step. This problem with the analogy is irremediable: if the argument is that brains are conscious because neurons are conscious we have once again committed the hard-to-avoid error of including something mental in our purported recipe for the mental. If not, then the analogy does not go through: the wood molecules and the table share a property in common, so we do not have an actual example of a macro-property emerging from a micro-property (that is not to say that we couldn’t find such an example, only that this one isn’t it).
The second problem is more serious and to the point of the present discussion. Psychological predicates, as I argued at length in Chapter Two, are not predicated of brains or nervous systems but of whole persons. This goes for consciousness every bit as much as it does for intentionality. Brains no more feel or sense things than they think about or imagine things. Persons think and feel. Asserting this does not exclude me from the club of materialists in any way.
The crucial difference between intentionality and consciousness is that while intentional states are supervenient and therefore unexplainable through reductive materialism, phenomenal states are not supervenient and so a legitimate answer to the question “Why does it feel like that?” is “Because it is that specific physical body interacting with that specific physical feature of the environment (chocolate molecule, blue-reflecting surface, soft pillow etc)” – strict reductive materialism. We can say this, I think, even if we accept the argument that the question “Why does it feel like that?” is itself in a sense illegitimate since there is no way to fill in the sense of “that,” as Hume, Wittgenstein and the Buddhists argue. The basic insight is that having these conscious experiences is indistinguishable from having this physical body in this physical world.
There is only one sense in which we can coherently say that our own phenomenal experiences are in any way similar to those of other conscious beings, such that we can grasp a link between intentionality (universal among all intelligent beings) and consciousness (unique to each conscious being). In this book I have emphasized the distinction between intentionality and consciousness. The last chapter will explore the connection between them.