The relationship between the mind and the body is one of the philosophical problems that has never been adequately answered. The functioning of the mind remains, for the most part, a mystery, and its precise nature and origins are still matters of controversy. The essential question regarding the relationship is simple to explain. How does my physical body, composed of more or less the same organs as the person next to me correspond to my mental processes and thoughts, which I do not have in common with him Two main streams of thought on this relationship have emerged: dualism and monism. Dualism was the approach favoured by Descartes, and has at its core the indivisibility of the soul and the clear distinction between the soul (of which the mind is a part) and the body. A monistic approach to the mind / body problem is the belief that they are not distinct, and that the mind and the body are part of the same thing.
This usually takes a materialistic form-the mind is a physical substance in the same way the heart or lungs are. It is worth pointing out at this stage that dualists are unlikely to consider the mind / body problem in the sense that a corpse, being a body devoid of a mind, is proof that the two are distinct entities. Clearly, this is irrelevant: dualists, when referring to a body, are basing their arguments on a living one. What happens to the mind after the living body dies is another issue altogether. A central tenement of Descartes philosophy is the view that the mind / soul is immortal although it exists on earth inside a body, it is released after death to the next world.
A dualist, like Descartes, is of the opinion that the physical body, which the outside world sees, occupies space and is govern e by the laws of physics as much any other physical entity is. The mind, on the other hand, does not inhabit space, is therefore not governed by the usual natural laws, and can only be seen by itself. Descartes, when considering the relationship, did not think it was the same kind of relationship as a pilot in a ship, implying that the mind does not merely observe physical damage to the body, in the way a ships captain would, but it experiences it itself. The two are connected through some system designed to do this.
Descartes himself considered that the two entities were connected through the pineal gland, which sent and received messages to / from the body (qv). If this is the case, then one cannot consider a mind to both be an entirely separate entity to the body, and not be merely like the pilot. Furthermore, Descartes view is open to the criticism which was elegantly expressed by Ryle when he referred to it as the ghost in the machine. He claimed that it suggests there is a complex visible system called the physical body which has as an engine an invisible complex called the mind, which takes on a spiritual form, ever-present inside the body.
Indeed, Ryle is of the opinion that this form of Cartesian dualism is a category mistake, the meaning of which is explained by a simile with a tourist visiting Oxford, seeing the colleges and the libraries, and then asking where the university is. This is to say that Ryle considers the treatment by Cartesian dualists of mental events as separate to the other aspects of the body, rather than seeing them as just one part of the processes of the human. There is thus no categorical difference between mental processes and physical ones. Even so, Ryles criticism does not explain why the mind and its consciousness actually occur.
The chemical reactions, biological operations, and physical operations of the various components of the body are unlikely to create the mind as if it were a side effect. This would lead one to a discussion of whether free will could exist, and Ryle does not appear to be an advocate of determinism. However, if the immortality of the soul is discounted, then Ryles position becomes more tenable. The mind can thus be considered to be a separate part of the body; one which inhabits the brain.
Certainly, if the mind / soul dies with the body, it requires the body to think (for example, a constant supply of oxygen to the brain and so on). This interpretation, though, is still likely to degenerate into determinism, as any consideration of the mind being a physical object will. The relationship between the mind and the body is at its most confusing when the issue of sensations is considered. Descartes considers the sense of hunger he gets when his stomach demands food: why, he asks himself, does a feeling of the stomach tightening indicate this to him In the Meditations, Descartes tries to understand the relationship by suggesting that the nerves transmit the signals to the mind via the pineal gland. He describes the nerves as acting in a similar way to ropes pulling bells. At the most basic level, he is actually very near to the modern understanding of the nervous system, although it neither ends in the pineal gland nor does it operate mechanically (it is a system of electrical impulses).
This description of it by Descartes is introduced when he considers the phantom limbs which amputees complain are causing them pain. This is used by Descartes to suggest that interferences or disturbances from elsewhere affect the body whilst giving the mind confusing signals. This, though, does not explain how the mind sends signals in response to these messages in order to get a reaction. Although Descartes believed that some responses, like the jerking of a hand away from a hot stove, were automatically controlled by mechanical processes, thus removing the mind from the process, others were the result of animal spirits flowing from the pineal gland to the bodily part it wishes to control. If, though, the mind and the body are truly distinct, this aspect of the relationship becomes more difficult to explain. As with the pineal gland, the idea of animal spirits is not only discredited scientifically, but Descartes does not attempt to actually explain what they are.
With a mind separate from the body, the only way it could control a part of the body, either as a result of received sense-data or as a result of its will, would have to be through some form of psychokinetic activity. I can will my fingers to touch the keys on this keyboard, but there has to be some form of connection between my thinking of the necessary movement, and its occurrence. To say that the mind can merely will bodily parts to move is not enough: I can will my ears all I want, and yet they fail to wiggle. Moreover, to say that the mind operates its control over the body through psychokinetic energy is only a step away from saying that it can also move external objects. Even if it were denied this power, the stomach cannot be willed to stop digestion, for example. At any rate, the way the communication between the mind and the body still raises questions of what the mind does with the information it receives.
As has been mentioned above, Descartes considers that the pineal gland is where the interchange takes place, and, thus, one presumes, where the data is transferred to other parts of the mind for processing etc. Dennett has expressed this idea as the Cartesian Theatre, and argues that the mind does not function in one place as the model suggests. The mind, according to him, takes in information from the body and the senses but does not deal with it in one central place. The mind operates (to use a computer metaphor) on a parallel basis, rather than the serial basis, which the theatre model seems to require. Descartes considered the mind to be the only thing that cannot be separated from himself. This means that he considers that it is the essence of the mind to think.
Essence, to Descartes, means the properties of a substance or thing that cannot be removed from it without losing the concept of it. The essence of a thing contains only that which is necessary for it to exist. Descartes therefore considers that his essence is thinking, thus he cannot detach his thinking self from his essence. Descartes, though, does not suggest that having an essence entails existence: this is only true in the case of God. However, as Malcolm suggests, if he can perceives the essence of something, he can perceive the thing itself.
He can perceive thought, so he is able to perceive himself. The body is not at the essence of the person; it is an extension of it. Although it is possible to doubt the existence of the body, he cannot doubt the existence of his mental self (hence the famous cogito). Therefore, the mind is inseparable to him. Arnauld, though, argued that just because one can doubt the fact that a right-angled triangle can have the length of the hypotenuse calculated using Pythagoras theorem, does not mean that this property is not essential.
Using this idea, Arnauld argues that just because one can imagine oneself without a body, this does not make it an inessential part of me. Descartes, though, argues that this ignores the point he is trying to make: he is merely trying to see what constitutes his essence, and only by doubting all that is possible to doubt can he do this. Malcolm has rightly pointed out that the Descartes test for what his essence consists of is to see if he is aware of that property, which makes him aware of himself. Only thought fits this description. Therefore, they can be said to be different things.
The relationship between the mind and the body is too complex to even begin to explain in an essay of this length. Descartes considered that the mind, whilst being connected to the body through the pineal gland and able to send and receive data through the use of animal spirits and the nervous system. By todays standards this understanding is flawed, but much of the current theories are still either dualist ideas akin to this, or materialist, which carries the risk of determinism.  I hesitate to use the term genetic information for fear of over-complicating matters 375.