Disagreeing with Descartes

Rene Desartes

'Cogito, ergo sum.' This is perhaps Descartes' greatest logical deduction. However, he makes a big jump from, 'I think, therefore I am,' to believing that this makes introspection a valid path to truth. How does knowing you can think mean that you can or should trust your thoughts? It doesn't. It simply means you can think, and therefore must exist. This does not make your thoughts trustworthy; it does not negate the possibility of self-deception. In fact, at least in the case of Descartes, it creates a quintessential instance of self deception: according to Descartes, we are constantly deceived into thinking we have a body when really all that we are, in essence, is a mind that is separate from the physical world. This is pure self-deception. Why, then, does Descartes take this to mean that our thoughts are a reliable path to truth in and of themselves?

'Cogito, ergo sum,' was one of Descartes' 'innate ideas.' To me, these innate ideas are simply 'truths' Descartes was able to convince himself of through his 'rational thought.' This exemplifies the stance of rationalism, or the belief that logic and rational thought alone can provide a path to truth. Descartes thought that human rationality was infallible. However, rational thought alone can be deceiving. Our rationalizing abilities are not perfect. Utilizing only logic can lead one to outrageous and even contradictory conclusions. One example is Descartes' own 'proof' of God's existence.

The modern version of Descartes' argument for God is often called 'the ontological argument', and it is fallacious in the same ways that Descartes' argument is. In Descartes' argument for the existence of God, he commits the logical fallacy of reification, as did the realists before him. In his argument, he first asserts that he entertains perfect ideas. In this, Descartes commits the fallacy of reification by assuming that perfection is a real thing, that it can actually exist; and that, because he can conceive of it, it therefore must exist. He then asserts that there must be an outside entity that is the author of these ideas, and that this entity is perfect in every way, and that entity is God. In this, he also anthropomorphised the concept of perfection, therefore committing an anthropomorphic fallacy as well. The problem is, perfection is only a concept, and a subjective one at that. It has never been empirically observed, nor has it ever been shown to be a universal or transcendent entity. One's idea of perfection is almost always different from another's. So, why, through his system of methodological doubt, did Descartes not doubt the existence of perfection?

In addition to the obvious fallacy committed in his argument for a perfect God, Descartes' notion of an entity that is perfect in every way is also not logically tenable in and of itself. Omnipotence itself presents a paradox in that one cannot be all powerful in every way; this is often expressed in the slightly comical quandary, 'could God create a rock so large that he himself could not lift it?' The ability to do some things necessarily excludes the ability to do other things, it is therefore impossible to be all-powerful. Another inconsistency is the notion of omniscience. It is impossible to know everything, and know that you know everything. No matter how much knowledge you apparently have, one can never escape from the solipsistic-esque status of not knowing if you are being grossly deceived. One can believe they know everything, but one can never know that they know everything.
As if this were not enough, the notion of perfection gets even less tenable when omnipotence and omniscience are combined. One who knows everything past present and future (omniscient) is therefore powerless to change it (not omnipotent). Omniscience would negate any and all notions of free will, that of God and of man. If God is all-powerful and does have the power to change the future (omnipotent), then he must not have knowledge of what will happen until he himself decides what will happen (not omniscient). Both omniscience and omnipotence have the effect of nullifying the free will of humans, something that Descartes also believed in; the logical inconsistencies just keep piling up. The Greek philosopher Epicurus (341 BCE - 270 BCE) drew attention to the obvious untenability of a perfect God almost two-thousand years before Descartes posited one with his famous series of quandaries:

'Is God willing to prevent evil, but not able? Then he is not omnipotent. 

Is he able, but not willing? Then he is malevolent. 

Is he both able and willing? Then whence cometh evil? 

Is he neither able nor willing? Then why call him God?'

Despite the obvious irrationality of Descartes' assertion of a perfect God, he goes on to deduce that because God exists, and is perfect, he would then not deceive us. Through this, he claimed to deduce that empirical observations via the senses could be trusted, to a point. He still warned, however, that perceptions could be deceiving, and that they should always be filtered through one's rationality to ensure validity. While I agree with what Descartes asserts here regarding a healthy check-and-balance system between empiricism and rationality, I do not agree with his reasoning leading up to the assertion as it is fallacious. Also, I would add that empiricism should be a check to rationality as well, especially in this case; if Descartes would only stop for a second, he would realize the inconsistency between his 'rational' assertion that God would not deceive us and his empirical observation that perceptions can be deceiving. One of these is wrong, can you guess which one?

Descartes seemed to be headed in the right direction with his theory of the reflexes. He posited that physical processes could account for all of animal behavior and a large portion of human behavior. He, however, made a sharp turn towards the supernatural when filling in that gap of human behavior which he believed could not be explained by physical processes. In the past, religions have 'filled in the gaps' of knowledge with various supernatural phenomena, such as explaining lightning with 'Zeus the lightning God,' and the such. To this day, arguments are made for the existence of God that run along the same vein of reasoning. A proponent of a religion will identify a gap in the knowledge of humans and quickly and unhesitatingly 'fill the gap' with their specific brand of God. This argument is therefore called the 'God of the gaps' argument, and is a logical fallacy. Asserting a supernatural entity in order to explain a natural phenomenon is a non-answer.

Like God of the gaps arguments before (and after) him, Descartes commits the same fallacy, the same lapse in logical judgment. In fact, nowhere is man's tendency to fill gaps with supernatural explanations more brilliantly displayed than when philosophers of the past placed cognition in the 'gaps' of the brain (the ventricles). Descartes' may be the most illustrative example of this: he literally filled the gaps of the brain with supernatural 'animal spirits' in an attempt to explain how the reflexes worked.

Where did he get the idea of animal spirits from? Did he get it from his own trusted methods of methodological doubt, intuition and deduction? No, it was a traditional belief which he adopted for his purposes; he filled the gaps in his theory with something that was easy for people to believe in at the time, but impossible for anyone to actually understand. So, Descartes' methodological doubt was strong enough to question the existence of the physical world, but not enough to bother questioning a nonsensical traditional belief for which there was no reasoned argument or evidence. This seems quite illogical and credulous for a man so obsessed with logic and skepticism. Today we have the law of parsimony built into our philosophy of science for the very purpose of avoiding such assertions of supernatural explanations which often make things more complex and enigmatic rather than simpler and more accessible to human reasoning.

Descartes seems to have got the 'I' part of 'I think, therefore I am' wrong in that he thought that 'I' was a transcendent entity of some kind. With his take on the mind-body problem, Descartes commits the logical fallacy of reification, again. This is because he says that: since he can imagine not having a body, then it must be possible to exist without a body. He then goes further to say that: because he cannot imagine not existing, then (when combined with the former) he must exist independently of his body. The problem with this argument is that the assumption that it is possible to exist without a body is a notion only realized through the logical fallacy of reification, making the entire argument fallacious.

There is no logical reason to believe that you can exist without a body; just because you can imagine doing so does not make it possible. One can imagine a great many things that are impossible, and imagining those things will never make them possible. Why, then, would imagining existence without a body make such a thing possible? Not to mention, just because Descartes could not imagine not existing does not make it impossible to not exist, especially at a later time.

Despite the flaws in his logic, Descartes was, no doubt, a highly influential thinker. Much intellectual debate following Descartes centered around his theories, whether opposing them or supporting them. The debate he inspired allowed for scientific progress in a form that would not have happened if not for him. This just goes to show that, as Popper said, a theory need not be correct to be useful; but rather wrong theories tend to prove most useful in scientific progression.