In the course of his ongoing debate with Dr. Stephen Novella on the topic of dualism vs materialism, Michael Egnor elaborates on the concept of "intentionality." There are different ways to think of intentionality, but basically it's the aboutness or meaning we attach to things. Egnor argues that meaning is a property of mind, not of matter and that the fact that we experience intentionality is strong evidence that there's more to our cognitive apparatus than just our material brain.
Materialist Paul Churchland sums up the materialist view that there is no immaterial component to us, no mind, this way:
The important point about the standard evolutionary story is that the human species and all of its features are the wholly physical outcome of a purely physical process...there seems no need, nor room, to fit any nonphysical substances of properties into our theoretical accounting of ourselves. We are creatures of matter. And we should learn to live with that fact.
For materialists of Churchland's stripe mind is only a word used to describe what matter (the brain) does. It's a word that describes the brain's function, like the word "photosynthesis" is a word that describes what green plants do. You won't find in a plant any photosynthesis (PHS), you'll only see chemical reactions occurring which we label PHS.
We are merely brains, Churchland believes, and our beliefs, hopes, and experiences (which comprise our intentionality) don't really exist at all except as chemical reactions in the brain. Your belief that you are reading this is simply a product of certain combinations of atoms, like the light given off when you strike a match, and if you had a different chemical reaction when you read these words you'd have a different belief.
Egnor says that the problem with this kind of materialism (called eliminative materialism) is that it's essentially self-refuting. How, he asks, can one believe that there are no beliefs?
If eliminative materialism is true, then a discussion about eliminative materialism is merely changing chemical gradients in the interlocutors' brains. Some materialists are willing to eliminate the mind in order to deal with intentionality. For these philosophers the brain is just a computational device, like a very special kind of computer.
But meaning is not a quality possessed by calculating devices like computers. Computers don't reflect upon what their computation is about. Egnor invites us to...
Consider a simple electronic calculator. It computes, in the sense that I can enter 2...+...3...= and I get ...5. It's amazingly accurate, fast, and reliable. The reason for its accuracy is that it employs a causal string of electronic events such that pushing the '2...+...3...=' buttons causes the event '5' on the little screen. Integrated circuits, all that stuff. Of course, the calculator doesn't think (really quick) "hmmm...two plus three is....hmmm...five!" There's no thinking at all. There isn't even any 'arithmetic' going on in the little calculator. There's just causal events, electrons bumping electrons and going through gates on a circuit, structured by the program to cause 5 on the little screen when 2...+...3...= is pushed. What's going on in the calculator is a mechanism, a series of causally effective material events.
Note that the actual meaning of the numbers and arithmetic operations doesn't really matter. My toddler can push 2...+...3...=, and still get 5, without any meaning to the computation at all. 5 comes up just because it is caused materially by the physical events. My cat could push 2...+...3...=, and still get 5....the computation is completely independent of meaning.
To illustrate the lack of intentionality or meaning in a computer John Searle constructed the problem which came to be known as the "Chinese Room." Searle's illustration is as effective answer to the idea that our mental processes are just computational events such as a computer performs:
Imagine that you go to China, and get a job there. You speak only English, and don't know a word of Chinese. You work in an information booth, in which Chinese people can write questions on a piece of paper and pass the question through a slot to you inside the booth. You of course have no idea what the question is, because you can't read Chinese. However, the Chinese guys that hired you have given you a book that has written, all in Chinese, any question that could be asked, and along with it, the answer corresponding to each question. You take the question written on the paper and search through the book, until you match the Chinese characters exactly. Then you copy the Chinese answer, and return to through the slot.
The Chinese person who asked you the question believes, quite understandably, that you understand Chinese, understood the question, and were smart enough to figure out the answer. And of course, that is true of the Chinese guys who wrote the book. But it most certainly is not true of you. You don't know Chinese, you don't know what question was asked, and you don't know what the answer was.
A Chinese person outside the booth would have believed that he was interacting with a person who understood his questions and provided good answers. But what you have done is, precisely, a computation. You have mechanically matched input to output, just as a computer program does, but you have added no meaning. You understand nothing. Only the minds of the guys who wrote the Chinese book have intrinsic intentionality. Computation-by-itself does not give rise to intentionality.
Meaning is not inherent to computation, no matter how complex the computation. Material causation - silicon-based computation in an electronic calculator, or tedious illiterate computation in a booth in Beijing, or carbon-based computation in a living brain - does not give rise to intentionality. Matter ... does not give rise to intentionality. Intentionality - meaning - is the mark of the mind.
If there is something immaterial about us, like a mind, that fact raises a host of additional questions. Where does it come from? What's its relation to the physical brain? What laws does it obey? What happens to it when the body dies? Etc. No one knows the answers to these questions, indeed it's hard to imagine how they would even be investigated. At this point, however, it's enough of a task to determine whether there are good reasons to believe that such an immaterial substance, one that plays a role in human consciousness and cognition, actually exists.RLC