Descartes first wave of doubt concerns sensory fallibility. Descartes states that ‘everything I have accepted…. I have learned from or through the senses.’ This, Descartes states, included the laws of mathematics and geometry, because we learn, initially at least, about these laws through the senses. He proceeds to doubt the reliability of these sense experiences in this passage ‘sometimes the senses deceive us, concerning things which are barely perceivable or at a great distance.’ Descartes uses this as evidence that we can be mislead by many of our sense experiences. Another good example of this kind of unreliability is AJ Ayer’s bent stick in water. When we look at a stick in a jug of water, the refraction of light causes the stick to appear bent, even though a common sense approach dictates that we know it is really straight. If we follow Descartes method of attaining knowledge, this level of doubt about our sensory experiences means that we can view them all as false for Descartes’ purposes.
Descartes does not allow things to be quite this easy however. He admits that there is a great difference between being mistaken when you see something far off in the foggy distance, and something immediately I may not be sure if that is Wayne Rooney in the distance on a snowy winter’s night, but I sure as hell would if he was staring me in the face. To counter his own counter as it were, Descartes introduces his second wave of doubt. Descartes argues that we could merely be asleep at this very moment and not realise it. But surely reality is far more ‘clear and distinct’ than a dream. I for example, am surely more lucid and aware of my surroundings at this moment writing this essay than I ever could be in a dream. However, Descartes rightly points out that we are only aware of this after we have woken up from the dream-we do not realise while we are in the dream that things were amiss. Descartes uses this to form the hypothesis that it is possible that he is in a dream right now, we are just not aware of it, and that at any moment he could wake up and think what a funny thing it is that he was doing that strange made up dream imagining called philosophy.
The possibility that he is at this very moment in a dream state seems to place all our sensory experiences, even ones which are right in front of us, totally into doubt However, in his quest for knowledge and a water tight argument, Descartes again adds another caveat. He states that even in a dream we cannot make up entirely new things, merely composites of other things. So while it is legitimate through the use of the dream argument to doubt complex things like science or philosophy, we cannot doubt the simplest concepts like mathematics and geometry. These simple building blocks are adventitious-they come from outside and are put into our ‘dream world’. In dream or reality, Descartes admits, two plus three will always equal five.
This leads Descartes on to his third and final wave of doubt. Descartes begins by asserting his belief in an all powerful, all loving deity who would not allow us to be deceived about our beliefs about the external world. However, it is surely against his all loving nature for Descartes to be deceived some of the time, and yet he allows this. Resolving that he must take his scepticism to some may say implausible lengths, Descartes supposes that there is ‘some evil demon, no less cunning and deceiving than powerful, who has used all his artifice to deceive me.’ This demon, Descartes things could be using his cunning to make Descartes believe that two plus three equals five when really it equals six.
It seems at this point to Descartes, and indeed to the reader who has been on this whirlwind trip of doubt with him, that Descartes has conclusively proven that nothing is certain. However, there are a number of criticisms of Descartes method of doubt which are essential to realise in order for it to be evaluated properly. One relates to a statement in this very paragraph-‘proven that nothing is certain’. This was first identified as a philosophical problem of global scepticism, because if you end up dedicated to a position that nothing can be known, then you know that nothing can be known. Whatever you believe therefore, there will always be something, however sceptical you set out to be, that you know. Some have claimed that this makes global scepticism an impossibility. On his part, Descartes does justify his use of logic later in the Meditations. He does this by appealing to God saying he allows us to safely believe in and use logic. However this quickly turns into what has become known as the ‘Cartesian circle’ as Descartes uses logic to prove the existence of God, creating a cycle where nothing gets resolved.
Whether you agree with this challenge to global scepticism or not, there is a much wider objection as to whether Descartes is a global sceptic at all. Some philosophers claim that if Descartes was setting out on a true quest of global scepticism then he would never have been able to write the Meditations at all, because this requires the abilities of reasoning, articulation and memory, none of which Descartes doubts he possesses in his apparently exhaustive quest for axioms. This in my view successfully takes away the possibility that Descartes could be considered a global sceptic, however it is often argued that perhaps Descartes, despite what he claims, never really aimed for this anyway. The premise of doubting everything was merely an enticement for the reader to come on this journey of discovery with him. I am inclined to agree with this assessment, not least because I believe global scepticism is an unachievable aim anyway.
Others, far from claiming that Descartes falls short of his aims, claim that he has set the bar too high. They claim that he has an unreasonable expectation of what knowledge is. Empiricists would claim that our sense data counts as knowledge even if it is not indubitable, and most everyday people would reject Descartes extreme scepticism about what knowledge is. However, from a purely philosophical standpoint I would accept Descartes view, however I think you should always beware the sceptic who sets an unreasonably high threshold for knowledge but does not take this scepticism into his everyday life.
An important area of evaluation is Descartes three methods of doubt itself. As I stated earlier they have not been immune from scepticism. George Dicker in ‘An Analytical and historical Introduction’ raised one objection. Consider this argument as an example: some paintings are forgeries. Therefore all paintings are forgeries. This is clearly invalid, as a forgery suggests that there is a real painting out there somewhere which the forgery is a copy of. Is Descartes not making the same mistake in his first wave of doubt? He argues that we are sometimes mistaken by our senses, and then makes the jump to saying that we are therefore always deceived by our senses. As we have seen through the forgery example, being sometimes mistaken by our senses means that sometimes we are not. As a contemporary American philosopher Maurice Mandelabaum said ‘one cannot prove that the senses actually do sometimes deceive us without assuming that they sometimes do not.’ Furthermore, how does Descartes assess that the senses are unreliable? By using his senses. His argument here is self-refuting, and in my opinion severely damages this first wave.
One major problem with the second wave of doubt is the way Descartes words it. He claims ‘there are no conclusive signs by means of which one can distinguish clearly between being awake and being asleep’ but then goes on to make a clear distinction between the properties of dreams and those of ‘reality’. This seems to be an example of either invalid reasoning, or at the least poor linguistic choice. Furthermore, the second wave of doubt can be criticised by the forgery example used to destroy the first.
However, the Importance of these two waves can be overestimated. Descartes merely uses these as a warm up to get the reader into his methods and involved in the process of doubt. It is the example of the evil demon which is really important, as this throws absolutely all of our knowledge into doubt. And unlike the other two waves, it is very difficult to logically object to this wave. Undoubtedly, it is extremely unlikely, but this is not the point-it is possible. The argument used is not self-refuting, and as with the more modern iteration of us all being brains in a jar being poked and prodded into the appropriate sensory experience, it is impossible to prove that it is not the case.
In conclusion therefore, I would argue that while it is an exaggeration to claim that Descartes is a global sceptic, and his method of doubt is far from perfect, in the most important area, the third wave of doubt, Descartes is successful, and we are forced to accept that just like Descartes, there is nothing which we could not for certain claim was not a falsity caused by a manipulating evil demon. In what Descartes set out to do, he is successful.
