How, according to Matthews, does Descartes's new concept of mind differ from that of his Aristotelian predecessors?
Explain any potential problems that Cartesianism gives rise to.

Matthews illustrates the differences between Aristotelian and Cartesian concepts of the mind by considering the case of Tik-Tok - a mechanical man that, according to its label, thinks but does not live [Matthews p122]. He first examines the Aristotelian view, which regards this idea as contradictory.

In the Aristotelian model, all things consist of matter and form. While matter is the physical composition of a thing, form is its shape, functionality and distinctiveness. Form is what makes a thing what it is [Crawford p24].

In the case of inanimate objects such as rocks, form may simply be the shape of the object. For something more complex, like a clock, form would be its functionality. For living things, form is the psyche - the soul.

All living things have a psyche, as this is what makes them living things. However, not all psyches are the same. There are three types. Plants have a vegetative psyche. They feed, grow and reproduce, but react and interact with the world only minimally. They cannot be said to be aware. Animals have a sensitive psyche. They have all the capacities of plants but can also perceive and interact with their surroundings. The highest form of psyche is the rational psyche, which only humans possess. In addition to the capacities of plants and animals, they also can judge and reason. [Crawford p25; CD1 track 3].

So, given that rationality is part of a rational psyche, and a psyche can only exist in a living thing, it follows that only living things can be rational. This means that Tik-Tok, who is not alive, cannot be rational, and therefore the statement "thinks but does not live" is a contradiction [Matthews p125].

Matthews now goes on to contrast the Cartesian view. Descartes, he says, does two things. He rejects the connection between living and thinking, and he rejects the separation between living and mechanical [Matthews p127; Crawford p28]. Thus Tik-Tok can be both mechanical and rational.

For Descartes, living bodies are conceptually no different from machines. Neither require any kind of animating soul to make them work. "it is not necessary ... to conceive of any vegetative or sensitive soul" [Matthews p127]. A living body may be far more complex, possibly even too complex for humans to fully comprehend, but they are the same kind of thing [Crawford p28]. Thus he could resolve the apparent contradiction with Tik-Tok by maintaining that just because it is mechanical, does not prevent him from being alive, and thus does not prevent him from being rational.

In these modern times, technology is progressing at a rate where concept of an artificial life-form is becoming increasingly plausible. Over two thousand years ago, Aristotle briefly considers the idea of mechanical toys, but it is not clear what, if any conclusions he comes to [Matthews p125].

Descartes goes on to maintain that a human is merely a biological machine with a rational mind attached to it - the so-called "ghost in the machine" [Crawford p55]. However, this rational mind can exist separately from a human body, and could in theory be tied to a mechanism other than a human body - for example a mechanical man. Tik-Tok could indeed be non-living, and yet still have a mind. He could indeed think but not live.

For Descartes, not only does mechanical not necessarily imply not-living, but not-living does not necessarily imply not-thinking.

Matthews next examines Descartes's view of the self - what constitutes "I".

In the Aristotelian model, I am a union of matter and form. Form cannot exist without matter, and so my mind cannot exist apart from my body. My body is as much a part of what is me as my mind [Crawford p25; CD1 track 3].

Thomas Aquinas, keen to unite Aristotelian philosophy with Christian doctrine about the immortal soul, suggests the mind can continue to exist after the death of the body, but only in a vastly reduced state. Without the sensory input of the body though, it cannot perceive or even imagine. It merely subsists until reunited with the resurrected body [Crawford p30].

Aristotle himself toys with the idea of thought existing apart from the body. "in most cases it seems that none of the affectations ... can exist apart from the body" [Matthews p131]. While far from conclusive, he appears inclined to believe that a disembodied mind would be far from a complete person [Matthews p131].

Descartes explicitly rejects this. He is not "a collection of members which we call the human body" [Matthews p130] but rather "a thing that thinks" [Crawford p34], i.e. a mind. A mind is complete and self-contained. I can exist without my body and I would still be wholly me. I can doubt everything I perceive, but I cannot doubt that there is an essential "me" perceiving them.

Descartes sharply separates mind and body into two distinct substances. He takes everything associated with the self - thought, character, awareness etc. - and lifts them out of the material body, creating an immaterial concept we now think of as "consciousness" [Matthews p132]. Ideas previously regarded as part of the soul he relegates to mechanical functions of the body [CD1 track 3]. He also takes ideas that had previously been thought of as part of the body such as perception and sensation, and includes them in the mind. While the body might be receiving physical stimulus and relaying it to the brain, it is the mind that interprets these signals and makes judgements based upon them.

For example, a number of photons bounce off an object in front of me and end up hitting my retina. This fires off various signals in the optic nerve, which in turn stimulates an assortment of neurons somewhere in my physical brain. These signals are now transmitted from my material brain to my immaterial mind where they trigger ideas. I become aware of the ideas, analyse them and judge that there is a coffee mug in front of me, and that it needs refilling.

A number of problems arise as a result of these ideas. Perhaps the most immediately apparent is exactly how are signals passed from the material brain to the immaterial mind? [Crawford pp37-38, CD1 track 5] However, just because we don't know how this particular step works is no reason to dismiss the whole theory. We still don't fully understand how gravity works, but that's no reason to dismiss Newton's laws.

Another problem is that, if we can doubt the existence of the external world, we can doubt the existence of everyone in it. I can only prove my existence as a conscious mind, and even then I can only prove it to myself [Matthews p134, p55]. Again though, this is not reason to discard the theory, and proofs do exist to demonstrate that the external world is real. More problematic is the issue of where sensation comes from.

Descartes divides sensory response into three grades: physiological, sensation and judgement. Consider the case of pain. Nerves relay the signals indicating heat (physiological), I am aware of the pain (sensation), and I decide I should take my hand out of the fire (judgement). Now, while nerve signals are physical and judgement is mental, sensation could be either. To put it another way, is the transition from physical to mental between nerve signal and sensation, or between sensation and judgement?

If sensation was physical, it would undermine Descartes's idea that he could be existing as a disembodied mind. While he can doubt the validity of his sensations, he cannot doubt their existence [Crawford p34]. "still it is at least quite certain that it seems to me that I see light, that I hear noise and that I feel heat" [Matthews p132]. If sensations originate in the body, then his body must exist. As the idea of being able to doubt he has a physical body is fundamental to Descartes's philosophy, he must reject this possibility [Crawford p41; CD1 track 5].

Therefore, sensation must exist in the mind. However, this means that only beings with minds - rational beings - can have them. Non-rational animals can have nerves firing signals all day, but they will never experience any sensations. They cannot experience pleasure, tiredness or pain [Crawford p40; CD1 track 4].

This may seem highly counter-intuitive, and some might consider it a knock-down argument, but Descartes instead bites the bullet. He maintains that what appear to be yaps of pleasure or yelps of pain are merely mechanical responses. "in animals it is these movements alone which occur, and not pain in the strict sense" [Crawford p45]. Of course, no matter how counter-intuitive it may seem to us, until we can see the world from within a dog's mind, we will be unable to disprove it.

These then are, according to Matthews, some of the differences between Aristotle's and Descartes's concepts of mind, along with some of the problems that Cartesianism gives rise to.

Bibliography

• Sean Crawford 2005. Aspects of Mind; Open University
• Gareth B. Matthews 1977 Consciousness and Life; reprinted in Sean Crawford, above.
• Audio CD 1 Thought and Experience.
• Rene Descartes Meditation II; reprinted in Robert Wilkinson 1999 Minds and Bodies Open University.