Part I: Can the mind exist without matter?
In the first part of this two part blog entry I would try to argue that all our conscious activity must correspond to definite physical changes in the brain. In other words if neuroscience were to ever reach a stage such that all physical changes in the brain could be observed and monitored (a goal that may be practically unattainable) we should be able to tell what a person is seeing, hearing, feeling and thinking by simply observing her brain.
Neuroscience may be far from reaching such a stage but discoveries already made in the field strengthen the case for the above proposition.
In a 2002 study British neuroscientists asked subjects to look at photographs of real faces and objects. Using fMRI, a technique which uses MRI scans to locate active regions of the brain by detecting increased blood flow, they identified regions of the brain (see figure on the right) that are active when a person looks at a face (marked fg) and the regions which are active when he looks at an object (marked pg).
The subjects were then shown Rubin's famous Vase-Face illusion (see figure on left). By simply looking at which regions were active in the MRI scans the scientists could predict whether the subject was perceiving the image as two faces or as a vase!
You may be thinking that while discoveries like this (see V S Ramachandran's BBC Reith lectures for many other equally fascinating examples) are definitely suggestive, my initial proposition is still a big extrapolation if it is based only on such findings.
There is in fact a more fundamental reason for my belief, a reason that I have learnt to appreciate because of my training in physics. A physicist would view the brain and its functioning as an extremely complex natural process. Physicists have a simple approach when they try to understand complex natural phenomena. Just as any change in the picture on your computer screen is brought about by a change in the colour and intensity of each of the pixels, any process that we observe in nature is the result of a change of the arrangement of smaller particles like atoms that constitute everything. As there are billions and billions of them in even a small object, simply by moving from one place to another, these particles can accomplish wonderful things- the rusting of iron, the burning of paper, the discolouration of leaves in autumn, lightning, tornadoes, in short everything you see around you! All the complexity in natural phenomena is because of the large numbers of these particles involved in these processes (a screen can generate a far more complex picture if there are thousands of pixels instead of say twelve). The movement of these particles is governed by precise, empirically tested laws. Based on the present state of a system of particles these laws tell us how the system will evolve in time.
The functioning of our brain is undoubtedly more complex than the phenomena mentioned above but our bodies and brains are made of exactly the same atoms that physicists and chemists study in the lab everyday. How these atoms evolve with time is governed by the same laws. Therefore it follows that what we will do in the next moment depends on the physical behavior of the atoms in our brains at the present moment (which might correspond for example to a high level of activity or increased blood flow in a certain region of our brain or may be an unusually large number of neurons firing in another region). But we also know that what we will do in the next moment depends on what we are thinking and how we are feeling at the present moment- if you are angry you might yell at someone, if you are depressed you might call a friend etc. Consider the two italicized statements in this paragraph. As an effect cannot have two different causes these statements suggest that what we subjectively feel as an emotion like anger or sadness corresponds to a definite behavior of atoms, i.e. a definite physical process in the brain that can be, in principle, objectively observed.
So at the end of this part the partial answer to the question posed in the title seems to be that any mental activity must correspond to definite physical processes in our brain and these physical processes can be analyzed using the usual methods of science. I will argue in the next part of this post that a scientific description of the objective process that a thought, emotion or sensation is related to is, however, inadequate in capturing all aspects of our consciousness.
The concept of consciousness not tethered to a body is obviously meaningless from this point of view. Thus from this perspective the idea of ghosts or spirits or a soul that leaves the body after death is absurd! The same thing can be said about a nirakar (formless) God having conscious attributes like mercy and forgiveness. But then rules need not apply to God!