The mind is a subject about which very much theorizing, experimenting, and expostulating has occurred in philosophy (studied under the heading philosophy of mind), psychology, and religion (where, in theology, it is often considered alongside such related notions as soul and spirit). Some people think it is synonymous with the brain. For some theorists the mind is the software of a brain, and the mind-body problem can be understood as analogous to this software-hardware connection. Others, such as the philosopher John Searle, say that the mind or consciousness is not a analogous to a program, but instead, is a property of a biological system, much as wetness is a property of water.
Substance or bundle?
There is a popular problem in philosophy about what the mind is, which can be presented as follows. It is commonplace to wonder what the mind, or soul (if you will), is. One can identify individual thoughts, individual feelings, in one’s mind. But what is this mind that has these thoughts and feelings? One can imagine all sorts of mental goings-on, but what is it to imagine the mind itself? It seems the only way we have of understanding, by introspection, what our minds are is by considering various particular thoughts, feelings, decisions, and other events in our minds (i.e., mental events).
So, someone might boldly maintain that we really do not have a mind, or a soul, per se–at least, we do not have any mind or soul that is distinct from our thoughts, perceptions, and other mental events. All there are is a series of thoughts and feelings that are associated with our bodies. There are no minds that are something over and above these thoughts and feelings. This would be the view of someone who held a bundle theory about the mind. The Scottish philosopher David Hume held a theory of mind like this. Buddhism holds a very similar view.
The view of common sense, it seems, is opposed to a bundle theory of the mind. We seem to have a mind, or soul, which is distinct from our thoughts and feelings–and that mind is just exactly what we call our selves. Hume seems to want to deny that there is such a thing as the self. To some people this seems absurd. To them, a substance theory of mind will seem more attractive. On this view, one holds that there is something–one may not know what, but something–which has the thoughts and feelings, and the thoughts and feelings are in our minds, in about the same way that properties inhere in a substance.
Philosophers have not infrequently bandied the phrase “mental substance,” and indeed, it has been made central to the ontologies of several philosophers, including most notably Gottfried Leibniz; according to Leibniz, the monad, a “simple soul,” is that in terms of which everything else in the universe was to be explained. The notion of mental substance is also basic to the dualism of René Descartes. David Hume was very famous for advocating a bundle theory of mind.
Psychological experiments on mind-body relations
In a study by Benjamin Libet, patients were asked to flex the index finger of their right hand suddenly at various times of their own choosing while the electrical signals in their brain were being recorded on an EEG. It was found that there was a gradual build-up of recorded electric potential for a second or a second and a half before the finger was actually flexed, indicating that the unconscious mind had made the decision before the conscious mind decided to act. Or, the actual initiation of volition may have begun earlier in some other part of the brain.
In another experiment on patients undergoing brain surgery, it took about half a second to register a stimulus applied to the skin, despite the fact that the brain would have received the signal of the stimulus in about a hundredth of a second and the pre-programmed reflex response takes only about the tenth of a second.
However, it should be noted that mind and brain are two quite different concepts — the first implies an “inside out” look, the second an “outside in” look. We have little more than unprovable assumptions on how exactly the two are related.