What sort of distinction (if any) do you think can be made between the mind and the body? How can this distinction, or lack of it, be rationally justified?

From ancient times Man has wondered about mental states and whether they are separate from bodily states. In more modern times the body can be reduced to questions of the brain. Whether there is a distinction between mind and brain is now in question. The question is now about reductionism. Can the brain’s workings fully explain mental states.

Dualist ideas of a mind separate from the body in characteristics or form can be found in Plato's time. Plato's theories were based on ideas of justice. He proposed that the mind, or soul, could exist without the body. At the time of death a virtuous man will have his soul transferred to a body becoming his acts during his life, the same would hold for a depraved man. This metempsychosis was characterised by the three characteristics of Plato's soul being transferred to a not-necessarily human body.

Plato’s ideas of transient, possibly immortal, souls or minds could be just a hopeful wish for justice in some other life. Other philosophers of his age argued for a physicalist or materialist view of the world. Democritus could possibly have been the first to think of an atomic theory of the world, and that all things were made of these indivisible objects, including the mind.

The division of mental from physical properties evolved with Augustine's ideas of time and memory in the 4th Century. If time is the measurement of movement and only bodies move then the soul, being immaterial, would not know time. The soul receives impressions of the past and expectations of the future which act upon our attention of the present. In a sense Augustine’s thoughts on the soul were very existentialist, although Augustine believed in a God.

Still the belief in mind was bound up with religious beliefs in immortality and justice.  

Later Descartes led to a belief that mental and physical substances were different. The mind would outlive the body and that rationally this must be so. Descartes’ doubt led to the subjective idea that something must doubt. The mind may be deceived by its senses from the body, but it must think in order to doubt and reason. When a mind perceives something it uses reason as well as perception. The mind is making a judgement about things.

So ideas of the mind were now admittedly subjective experiences with faculties that were both intellectual and sensual. Still medical and scientific advances had not explicitly situated the mind in any part of the body.

Materialists, earlier Monists, believe that there are no mental states or substances that haven't a physical explanation. The Mind is a totally physical activity. Materialism has many things going for it.

All mental activity, or inner mental life, may succumb to Occam's Razor of a sufficient explanation in physical terms. There is an economy of explanation in ascribing neuro-chemical and neuro-physical processes within the brain to mental states. The brain may well be totally described in physical science terms. Mental states cannot be described as such because the measurability of mental states can be questioned. Atomic, molecular and cellular descriptions and explanations for other biological material such as other internal organs do not preclude the brain.

There are objections to the materialist views on the mind. One is to do with access. A person has more intuitive knowledge of their mind and its workings than their brain. In describing their moods, thoughts ideas in terms of mind can be more accessible than any description of the physical processes occurring in the brain. From this mental aspect knowledge cannot be denied, it is aspectual and accessible.

Brentano’s answer to the materialist’s description of the mind in physical terms of the brain involved Intentionality or ‘aboutness’. The subjectivity of the mind helps with describing the knowledge of beliefs that can be of non-existent objects or just plain misrepresentations of reality. There are aspects of reality that cannot be explained in terms of neuro-chemical processes in the brain.

Materialist answers to this objection by accounting for ‘aboutness’ in material terms. One answer has been that physical processes in the brain resemble the objects thought of.   This may be a future retort for mental objects that are visual in nature, but not for linguistic references to thoughts. The word ‘Mike’ does not resemble an 18 stone 40 year-old!   At the moment the patterns of neurological activity found by present imaging techniques in no way resemble the ideas that could be described by those imaged as thoughts.

Another answer to the aboutness objection is that any activity of the brain has been caused by an object or idea. This does not answer the problems of misrepresentation of ideas within the mind, nor ideas about non-existence objects (such as Unicorns?). It is false beliefs that any causal analysis may have trouble explaining in physical terms.Original or creative thought has not been explained in purely physical terms. One creative person may have an infinite difference in neurological processes from another subjectively equivalent creative person.Could creative thought be reduced and possibly replicated by measured amounts of neurological drugs?  Mental states leading to creativity may be enhanced by drugs but there is a rational element such as the juxtaposition of ideas that may need more than drugs to be acceptable.

Materialists attempt to explain all facts about mental states in physical terms. They attempt to reduce any description of mind into neurological terms. Mind facts are said to supervene on brain facts, so brain facts are the base of all mind facts.

There are mental states that can be described as such despite the medium that these states are situated on. There can be supervenience, but mental states and their descriptions could sit easily on other brains, (or even other mediums such as silicon chips?). The mental state and its description surpasses the materialist medium on which it is held in explanatory terms.

Knowledge of other minds has been identified as developing at the age of 4 or 5. Mental inner life may not start at the same time as physical, brain activity. A person’s brain may be fully developed, but are we fully sentient when born, or when?

There is a question of personal identity that is easier to explain in terms of mental states than physical descriptions. Expectations of life, knowledge of one’s impending doom and how to prolong life (if that is acceptable to the individual) and how to live it are all part of mental life. A belief, however unproven by physical facts such as brain-death, that part of one’s identity will survive is almost necessary for progress in life.

I follow Nagel’s worry about the total objectivity of materialism. It possibly leaves behind a wealth of explanatory material that is more subjective, such as the Mind, that could be just as meaningful. Intentionality has not been completely conquered by physicalist descriptions of the brain, and may never be completely. The part, however small, that still causes puzzlement for cognitive science, is the part that cannot be reduced and can only be explained in more subjective terms, such as mental states.

George Graham Philosophy of Mind, Second Edition, Blackwell 1998.