Does Descartes Succeed In Showing We Know Anything At All?

In his Meditations on First Philosophy, Descartes`s once-in-a-lifetime project of doubting what could be logically doubted aimed to challenge the accepted philosophical systems of scholars such as Aquinas and Aristotle and reassess how we can gain knowledge about the universe. After introducing his three reasons for doubt - the doubt of the senses, the dream doubt and the demon doubt - the Meditator is able to come to the undisputable conclusion, `I am, I exist` (Descartes, 1640: 18). Accepting this starting point as true, in my essay, I will evaluate how Descartes attempts to resolve the doubt of the senses in his Sixth Meditation and whether he succeeds in showing that we can know anything at all about the external world.

In order to resolve the doubt of the senses, the Meditator begins his Sixth Meditation with an account of the `real distinction` between body and soul. Having reached the conclusion that what we perceive clearly and distinctly can be trusted, the Meditator expands to follow the idea that if we can conceive of two things separately, then it is logically possible for them to exist as such. The statement, `I am, I exist`, could suggest that the only predicate of the self is that it thinks - while sense and imagination are properties of the self, they are not essential to it, and the self can be conceived of independent of sensory experience.

`I have a clear and distinct idea of myself, insofar as I am a thinking and not an extended thing, and, on the other, a distinct idea of a body insofar as it is only an extended and not a thinking thing, it is certain that I am really distinct from my body.` (Descartes, 1640: 55)

The Meditator extends his `real distinction` to attempt to account for the existence of material objects and, ultimately, resolve the doubt of the senses. According to the Meditator, while thought is an active faculty which the mind produces independently, we have no control over the passive senses. Because sensations such as taste and sound arise involuntarily, their cause must be external - the Meditator concludes that we either sense material objects because they actually exist, or because God caused them. As God is no deceiver, the sensations must come from the objects themselves.

However, although we can be sure of quantifiable properties such as size and shape, other, more subjective attributes, like taste or smell may not resemble external reality. The Meditator justifies these sensations by likening the divisible body to a machine and the mind to a pilot. Hunger, thirst and pain may not exactly resemble the external world, but simply inform the mind of any problems the body may be facing. Similarly, sensations such as colour and taste inform us about the world, but do not necessarily resemble it. In order to accurately interpret sensory data, we must rely on reason and understanding, as senses may represent the external world without necessarily resembling it. Through this reasoning, Descartes apparently resolves the doubt of the senses as outlined in his First Meditation, holding that we can avoid error through clear and distinct perception, and subjecting our senses to rational scrutiny.

However, there are a number of flaws with the Meditator`s reasoning throughout the meditation. Firstly, Descartes` initial conclusion about real distinction appears to commit the epistemic fallacy. Leibniz`s Law follows that if two things are identical, they must share the exact same features. However, as Descartes does not know all of the properties of the mind and the body, he cannot reliable comment on their interconnectedness. For example: I cannot doubt that A is F; I can doubt that B is F; therefore A and B are not the same. However, not knowing the full properties of both A and B, it would be invalid to make such a claim. Norman Malcolm gives the example,

`If it were valid to argue `I can doubt that my body exists, but not that I exist, ergo I am not my body`, it would be equally valid to argue, `I can doubt that there exists a being whose essential nature is to think, but I cannot doubt that I exist, ergo I am not a being whose essential nature is to think.` (Vardy and Arliss, 2003: 130)

Furthermore, the idea of existence without a body does not appear to be logically sound. While Descartes argues that the body is not essential to the self, he does not speculate on what form the soul might take without a body. With no organs, dimensions or way of experiencing the external world, what exactly exists, if not a body? In the Fifth set of Objections, Gassendi raises the problem of interaction; Although the Meditator claims that the body and soul are connected, he does not explain how this might be possible. `How can you , the mind, be united to the body.without being extended? If you are not a body, how can you impart motion to a body, when motions can be transmitted only by contact?` (Descartes, 1640: 179)

Descartes replied to this objection, claiming that

`The mind is united to the whole of the body, but this does not mean it is extended through the body.` (Descartes, 1640: 198)

However, this response fails to explain how exactly the mind is `united` to the body. Gilbert Ryle famously rejected the idea of `the ghost in the machine` as a `category mistake` (Baldwin, 2001: 45), as something immaterial being connected with a physical substance is incoherent. In his Meditations, Descartes`s dualism appears to be unsupportable as he offers no convincing response to the problem of interaction.

The influential empiricist David Hume also rejected Descartes` real distinction in A Treatise of Human Nature, instead favouring the `bundle theory` (Dicker, 1998: 18), which holds that an object is the sum of its attributes. To Hume, existence itself is defined by the properties of an object - if a tomato ceased to be the size, shape and colour of a tomato, and lost its properties such as edibility, it would cease to be a tomato.

Similarly, a person is the sum of their parts and so the idea of an immaterial inner "self" is, to Hume, implausible.

The analogy of the wax, found in Descartes`s Second Meditation, could counter this theory as, having lost its external properties, the wax is still recognisable. According to the Meditator, it has retained an underlying essence which the soul continues to recognise in spite of different external properties. However, Hume refutes this idea, claiming that in order for us to perceive such an essence, we must still ultimately turn to the senses. If we recognise the wax in spite of its external properties, then we do so by using the senses and observing any changes in the object. Hume`s theory seems to be valid, as we do not intuitively recognise facts about the world - such as ice being frozen water - but learn through sensory observation.

Even accepting Descartes`s dualism as true, his conclusions about the external world remain flawed. In particular, the idea that the cause of any passive experience must be external does not account for dreams or hallucinations which seem to be the product of the mind alone. Modern psychology could also be used to refute Descartes`s claims, with its focus on the importance of a subconscious. While the mind is capable of active thought, there are also many passive faculties of the mind, and so perhaps Descartes`s reasoning behind the idea of an external world is logically unpersuasive.

In addition, much of Descartes`s argument revolves around the idea that God is no deceiver and would not plant sensations directly into our minds - an idea he explored in his Third Meditation. However, Descartes seems to be making many presumptions about the nature of God - why must god be perfect rather than malevolent? Even if we were to accept the idea of God as perfect, we have no evidence to suggest that a perfect God would not implant images of an external world into our mind, as our standards of what is good may differ from those of an omniscient, omnipotent and infinite being. In presuming to know the nature of God, Descartes`s account for material objects fails.

Having reached his first conclusion, `I am, I exist`, much of Descartes`s Meditations is dedicated to resolving the doubts laid out at the beginning of the process, and the attempt to prove that our senses at least give us some idea of the external world, even if inaccurate, is an important step for the Meditator. Having failed to resolve this doubt using reason alone, Descartes may also have failed to show that we can know anything at all, as his reasons for doubt are so challenging. However, in spite of his later conclusions, Descartes bedrock truth appears to be undeniable and so, if nothing else, is able to confidently state, `I am, I exist`.

Bibliography Baldwin, Thomas 2001 Contemporary Philosophy: Philosophy in English since 1945 (Oxford University Press) Cottingham, John 1986 Descartes (Blackwell Publishing Ltd: 2003) Descartes, Rene 1640 Meditations on First Philosophy (Trans Michael Moriarty, Oxford University Press: 2008) Dicker, George 1998 Hume`s Epistemology and Metaphysics: An Introduction (Routledge: 2003) Vardy, Peter and Arliss, Julie 2003 The Thinker`s Guide to God (John Hunt Publishing Ltd)