Global scepticism puts all of our attempts at seeking true knowledge into doubt; it makes all traditional ways of finding out about the world unreliable. One of the most famous sceptics is the philosopher Rene Descartes. In his first meditation, Descartes regards the ‘many false things’ that he had once believed as a child and acknowledges that all his beliefs were built on things that can be doubted. Descartes believed that he would have to start again on more solid foundations than those more doubtful ones his knowledge was previously built on.
It is through Descartes’ acceptance that all his current knowledge is doubtful that makes him a sceptic, however even Descartes hold the view that he will still be able to rebuild his knowledge once he gains more solid foundations. Descartes put forward three waves of doubt, the argument from illusion, the evil demon argument and the argument from dreaming. Descartes believed that each of these ‘waves of doubt’ forced him to question all the beliefs that he held.
Descartes believes, in his argument from illusion, that our senses sometimes deceive us; for instance, when I look at a drinking straw in a glass it appears bent, yet when I remove the straw from the glass it is straight. Descartes argues that if our senses have been proven to mislead us in the past, then we cannot be certain that they are not deceiving us now. This argument challenges our everyday beliefs; everything around us could simply be a result of our senses deceiving us.
Other philosophers criticising Descartes have argued that there are degrees of certainty. There are many things which can be doubted, but there are also things which cannot be seriously doubted, like the fact that I am currently in England. These degrees of certainty allow us to function normally, and discard any irrational doubt (i. e. if I get out of my bed this morning, will the floor still hold my weight or will I go through the ceiling? ).
Descartes ‘evil demon’ argument suggests that there is an evil demon which controls all of our thoughts and actions. This is very similar to the ‘brain in vat’ theory; the idea that we are simply brains in a vat of nutrients, wired up to a computer, controlled by an evil scientist, which sends the brain sensory experiences. It is very difficult to argue against this theory as it is hard to prove that we are not simply brains rather than living, breathing human beings, however some philosophers have argued against this ‘brain in vat’ theory.
If I am really just a brain in a vat, why would the evil scientist want me to question my existence, surely if the evil scientist was in complete control of all of my thoughts then I would not have doubt that the experiences I have a real. Perhaps I am a brain in a vat and the fact that I am questioning my existence means that the evil scientist is beginning to lose control over me, in which case my existence is not completely controlled by the computer.
If the evil scientist is completely deceiving me then why m allowed to express doubt, similarly, how does Descartes have any concept of deception if he is being controlled by an evil demon? Even if the theory is correct and we are just brains in vats, the evil scientist must exist in some kind of a world which is similar to the one created by the computer as the computer images we see must have been based on something real, and surely things which are logical in the world created by the computers must be logical in the world that the evil scientist exists in (two plus two will always equal four).
This means that although you cannot be sure that we exist in the ways we have believed ourselves to exist in, we still do exist in some form, in a world, even if it is just as a brain in a vat, this means that through the ‘brain in vat’ theory, it has still not been proven that global scepticism is possible. Descartes third wave argument from dreaming; if I dream one night, how can I be sure that my life is not just a whole dream, and that I have never woken up?
Is it ever possible to tell the difference between dreaming and reality? It has been argued that during reality, our existence has a certain structure, sequence and order unlike our dreams, and that we can look back on our dreams as memories, and analyse them, however, in the past I have dreamt that I have woken up, only to find that I am still dreaming. It is this kind of lucid dreaming that Norman Malcolm identifies as a problem. Does this mean that it is possible to be globally sceptic?
It is true that all claims can be asked for justification, and the justifications can themselves be questioned, and the answers to those questions can again be questioned and it the cycle of justification can go on forever if we are willing to enter into a never-ending regress of justifications. If we constantly challenged everything however we would appear impractical and mad to everyone else, and we would not be able to function probably due to our seemingly irrational doubts about ourselves and the world.
If then we ignored these sceptical doubts, in order to maintain the legitimacy of our beliefs, then would we not simply be accepting the fact that scepticism is impossible to answer. There are many philosophers (i. e. Barry Stroud) who believe that scepticism is unavoidable. Personally I believe that scepticism is unavoidable, but only to a degree, you cannot doubt everything (i. e. be a global sceptic) because then you would not be able to live at all, you would be too afraid that anything you might do would end in your death, therefore global scepticism is not possible.