“It is manifestly impossible to doubt… that I am in this place, seated by the fire, clothed in a winter dressing-gown…”
Due to this less radical first wave of doubt Descartes turns to a different argument of what is true knowledge, and what has the potential to be doubted.
So, Descartes turns to dreams, which he feels are a stronger protest to the certainties of senses. Could it be, he asks, that all our experience is part of a dream? How can we tell waking life from dreaming? It is possible that the objects we perceive as real are part of an elaborate dream? When you were a child it was common to get a ‘wet dream’; where you dreamt about going to the loo and relieving yourself in the pot, when in fact you were tucked away in bed, wetting your mattress! However, whatever happens in my sleep, can surely not be as clear as my actions now, in typing up this essay. Nevertheless, when I assess things carefully, I realise that there are no conclusive indications by which waking life can be distinguished from sleep, and I find that it is almost possible to convince me that I am dreaming. As Descartes puts it;
“…there are never any sure signs by means of which being awake can be distinguished from being asleep”,
For I could well be typing an essay in my dream. Descartes believes that dreams must have a basis in reality, as there are many elements of dreams that are the same as waking reality. In dreams (as in reality) the truths of mathematics and geometry remain the same. So 2+2 will always equal 4, as it does not seem viable that truths so clear can ever be suspected of any uncertainty. These priori’s are thus indubitable in both reality and dreams, and they therefore must exist. Hence Descartes rejects his second wave of doubt, as he does not believe that it allows him to doubt all that can be doubted.
The third wave of doubt is the most radical. Descartes believes that God exists, and that He is good. However, Descartes put the question of an ‘evil demon’ before us. He states that although God would not deceive us, this evil demon is very capable and likely of doing so. This demon is proficient at deceiving us, even about those things which reason find certain; the things which remain as certain in dreams, like geometry. Descartes insists that he could even bring it about that ‘there is no earth, no sky, no intended thing, no shape, no size, no place’ – but he could still warrant that us mortals on earth would believe that these things do in fact exist.
A more modern version of Descartes theory is the ‘brain in a vat’ concept. Imagine that you have no body at all and are only a brain kept separate from your body. All your organs of sense perception have been removed and you kept alive in a vat, through medical procedures. All your thoughts and feelings are the mere result of an evil scientist feeding information into your brain, and controlling all your functions. In this case you are nothing more than an elaborate mechanism which is capable of realistic action and emotion.
If such is the case, then Descartes is proposing that you do not actually exist. He is beginning to doubt everything, because, if this malicious demon does exist then one could never be certain of anything. However, the paradox of this theory comes in when Descartes realises, that in order to doubt your personal existence, you must exist. In other words, if one is to be deceived the must exist in the real world. Descartes explains this point by stating;
“he will never bring it about that I am nothing so long as I think I am something…I must finally conclude that this proposition I am, I exist, is necessarily true…”. Descartes has at last found something he considers indubitable – as long as he is thinking, he exists; or as long as he is doubting, he exists. The two famous Latin philosophies, “cogito ergo sum” (I think, therefore I am) and “dubito ergo sum” (I doubt, therefore I am), originate from Descartes quest to find something indubitable. It is known itself as ‘the Cogito’.
Descartes seems to know he exists, but he then goes on to ask what he is. Referring back to his evil demon argument, he says that although he thought that he, “possessed a countenance, hands, arms, and all the fabric members that appears in a corpse”, there could still be a malicious demon misleading him, to believe that this is so. So the question remains, what is he? What are humans according to Descartes’ beliefs and theories? In the end, he deduces that as long as we think, we exist. He naturally believes then that when we stop thinking (serious brain damage), we cease to exist. Therefore Descartes views us as thinking beings, and nothing more.
Nevertheless, Descartes still has not finished his search for everything that is indubitable. From there, he goes on to compare our knowledge of the mind to that of material objects. A famous example used to illustrate Descartes’ belief in reason, rather than senses, is the ‘wax tablet argument’. Here Descartes demonstrates, solely though reason, how reason unlocks the door to reality. Descartes takes up a wax tablet. He notes its properties: it is solid, it has a certain shape, and it makes a certain noise when hit and it has an odour. However, once he places it near a fire, the wax changes its properties completely.
Descartes major question is whether or not we are left with the same piece of wax? He abandons his senses and turns to his mind for reason, ultimately agreeing that this is the same piece of wax you saw a few moments ago, only, it has physically changed. He concludes that our senses change with the surface characteristics of the wax tablet. Our senses follow the empirical and are confused when confronted by change. Descartes believes that the senses reach an impasse, and can go no further in explaining what the wax is. They cannot tell us what the reality of the wax is. However, if we turn to reason we will find the reality of the wax. We will find that the melted wax is the same substances as the frozen one, only its physical properties have changed due to the heat. This is why Descartes says the wax is ‘perceived by the mind alone’. Now if we look at the way mathematics and geometry depict things, we find continuity and permanence rather than change. We find the perfect triangle which is what we work from, not impressions of triangles. So, in the case of the wax, we find that the wax has certain necessary truths or a priori truths. If we use the same reasoning about our mind we come to a rather different conclusion than we did with matter. The mind intuits the stability of matter or the continuity of things by reason alone. That an object can change over time does not spoil our knowledge of the object, it simply means that the object has certain necessary or a priori features and it also has certain accidental or a posteriori features.
It is plain to see that Descartes has made a phenomenal distinction between mind and body. The conclusion he has come to is that everything that is empirically observed, or in other words, everything which is perceived by the senses is false, but everything which is separate from the body and perceived in the mind is true, i.e. it is not subject to the senses’ weakness. It is also through the mind that you recognise your existence and not through the senses. As Descartes argues, so long as you think you exist, you really do exist, “I think, therefore I am”.