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There is a popular Philosophy 101/Philosophy of Mind argument that looks at the data from brains which have had the corpus collosum, which connects the brain's right and left hemispheres together, severed. Severing the corpus collosum was an old remedy for seizures which is no longer used, but the data remains. These brains had minds where one part of the mind did not know what another part of the mind was seeing. For example, the left eye would look at an apple but the mouth would say "I don't see an apple." The Analytic philosophers' argument is that a "person" or a "mind" is one whole being, and therefore the self cannot be identical with the brain. I draw precisely the opposite conclusion: it is scientifically undeniable that the mind is the brain, and therefore cognitive neuroscience must conclude that the mind/brain has many different parts, which work together in a healthy brain but which can become separated by physical or psychological dysfunction. Based upon reading about it and personal observations, I believe the brain has several distinct parts, which most people would recognize. The consciousness or "upper brain" is probably the frontal lobe of the cerebral cortex, possibly only the neocortex section. The consciousness is aware of reality and uses conscious reasoning. The "lower brain" or subconscious mind is probably many different structures, probably including both the other lobes of the cerebral cortex and structures in the middle of the brain including the amygdalae and basil ganglia. The lower brain uses subconscious reasoning, has emotional reactions such as lust or sadness, and also implements behavioral conditioning through feelings of reward and punishment. The "bottom brain" or unconscious mind controls bodily functions like digestion, and is invisible to the conscious mind.
I think that evolution intended for the conscious mind to "manage" the subconscious mind and to make a deliberate effort for the brain to function properly and for the different parts to work as a whole. The lower brain has a naturally short attention span and gets easily distracted by sensory stimuli or thinking about sex, and has the attention span of a fish--maybe 30 seconds before something distracts it. Concentration and focus come from the upper brain. The lower brain also has a natural tendency to be irrational, and I believe that evolution intended the upper brain to impose rationality upon the lower brain. Cognitive neuroscience indicates that the brain often functions by having biological impulses and urges which can be suppressed and inhibited by the action of the brain, and I think that the consciousness acts by controlling the lower brain and directing the brain's tendencies into a rational plan. Performing a task uses the entire brain, with the bottom brain interfacing with and moving the body, the lower brain using the habits conditioned from experience, and the upper brain paying attention and thinking about the task.
The human brain has a design flaw in that the consciousness naturally thinks of itself as a nonphysical "soul" and sees the lower brain as the "body." I dispute such a view of the mind. The consciousness is a part of the brain, and the mind is a physical object in reality, a "res extensa" to discredit Descartes using his own terms. The consciousness as brain does not mean that there is no such thing as free will. As stated, the brain can modify and influence itself by its internal cognitive processes, and the conscious mind can make decisions which control the lower brain. But the lower brain can also have physical malfunctions which impose irrationality upon the consciousness, which is how I would characterize mental illness. The self is not ethically responsible for mental illness which has an entirely physical origin, although it is the task of the upper brain to impose rationality upon the self, and it is also probably possible for a brain to freely choose to behave in an insane manner. Free will is "top-down" causation wherein the upper brain controls the brain's behavior, whereas mental illness is a type of "bottom-up" causation wherein physiological factors influence or control the conscious mind's thinking. Obviously this would be difficult to scientifically inspect using contemporary methods, but could be inferred from first person introspection. This is not so much a scientific postulate as it is a theory which could be called philosophy of mind/philosophy of science presenting a foundation for cognitive neuroscience.
