Amid a strongly critical (and therefore entertaining) book review of Ray Kurzweil’s How to Create a Mind: The Secret of Human Thought Revealed, Colin McGinn makes these observations about contemporary neuroscience in general:
Here I must say something briefly about the standard language that neuroscience has come to assume in the last fifty or so years (the subject deserves extended treatment). Even in sober neuroscience textbooks we are routinely told that bits of the brain “process information,” “send signals,” and “receive messages”—as if this were as uncontroversial as electrical and chemical processes occurring in the brain. We need to scrutinize such talk with care. Why exactly is it thought that the brain can be described in these ways? It is a collection of biological cells like any bodily organ, much like the liver or the heart, which are not apt to be described in informational terms. It can hardly be claimed that we have observed information transmission in the brain, as we have observed certain chemicals; this is a purely theoretical description of what is going on. So what is the basis for the theory?
The answer must surely be that the brain is causally connected to the mind and the mind contains and processes information. That is, a conscious subject has knowledge, memory, perception, and the power of reason—I have various kinds of information at my disposal. No doubt I have this information because of activity in my brain, but it doesn’t follow that my brain also has such information, still less microscopic bits of it. Why do we say that telephone lines convey information? Not because they are intrinsically informational, but because conscious subjects are at either end of them, exchanging information in the ordinary sense. Without the conscious subjects and their informational states, wires and neurons would not warrant being described in informational terms.
The mistake is to suppose that wires and neurons are homunculi that somehow mimic human subjects in their information-processing powers; instead they are simply the causal background to genuinely informational transactions. The brain considered in itself, independently of the mind, does not process information or send signals or receive messages, any more than the heart does; people do, and the brain is the underlying mechanism that enables them to do so. It is simply false to say that one neuron literally “sends a signal” to another; what it does is engage in certain chemical and electrical activities that are causally connected to genuine informational activities.
Contemporary brain science is thus rife with unwarranted homunculus talk, presented as if it were sober established science. We have discovered that nerve fibers transmit electricity. We have not, in the same way, discovered that they transmit information. We have simply postulated this conclusion by falsely modeling neurons on persons. To put the point a little more formally: states of neurons do not have propositional content in the way states of mind have propositional content. The belief that London is rainy intrinsically and literally contains the propositional content that London is rainy, but no state of neurons contains that content in that way—as opposed to metaphorically or derivatively (this kind of point has been forcibly urged by John Searle for a long time).
And there is theoretical danger in such loose talk, because it fosters the illusion that we understand how the brain can give rise to the mind. One of the central attributes of mind is information (propositional content) and there is a difficult question about how informational states can come to exist in physical organisms. We are deluded if we think we can make progress on this question by attributing informational states to the brain. To be sure, if the brain were to process information, in the full-blooded sense, then it would be apt for producing states like belief; but it is simply not literally true that it processes information. We are accordingly left wondering how electrochemical activity can give rise to genuine informational states like knowledge, memory, and perception. As so often, surreptitious homunculus talk generates an illusion of theoretical understanding.
