11/30 A Brief Introduction to Descartes’ Skeptical Arguments

Descartes, in the book Meditations on First Philosophy, gives us a battery of arguments for doubting the existence of the external world. We call these arguments his skeptical arguments.

  1. What these arguments are?

The skeptical argument is the first argument in Meditations. For he thinks he had accepted a large number falsehoods in his childhood and he regards them are true. Thus, the whole edifice that he had subsequently based on them is highly doubtful. So he says “I realized that it was necessary, once in the course of my life, to demolish everything completely and start again right from the foundations if I wanted to establish anything at all in the sciences that I was stable and likely to last”[1], to achieve this goal, he advanced a possibility method, “for the purpose of rejecting all my opinions, it will be enough if I find in each of them at least for doubt.”[2] Then, he started his arguments.

Firstly, Descartes doubted about the reality of the sense-perception. For it is obvious that senses may deceive us sometimes. However, for example, that I am here, sitting by the fire, wearing a winter dressing-gown, holding this piece of paper in my hands, and so on. How could it be denied that these hands or this whole body are mine? If we think that, maybe I am mad. So Descartes started the next argument.

Secondly, he illustrated the Dream Theory, in which we cannot believe our sense-perception because there are never any sure signs by means of which being awake can be distinguished from being asleep-perhaps, I think I’m reading on the table, but in fact I’m lying undressed in bed. When I am dreaming, I can also have such experiences and perceptions as I have a real body. Obviously, I have been cheated by these thoughts. Thus Descartes think we cannot ever find any sufficient reason to believe our sensory experiences to be true at all. However, some clever people may say, although it is hard to distinguish awake and asleep, everything in dreams are not imaginary but are real and exist, and they claim that some sciences are the same whether in dream or in reality, like Geometry, or some simpler and more universal things. This kind of scientific knowledge does not need sensory proofs to be true.

Then, Descartes thinks that in our minds, there is an omnipotent God makes us the kind of creature. But, how do we know the God won’t deceive us? He can make us have all senses although they do not really exist. Also, he makes us make mistakes in such 2+3 or count the sides of a square or even simpler matters are not unimaginable. Perhaps God would not have allowed me to be deceived in this way, since he is said to be supremely good. But sometimes, I do deceived; it seems inconsistent with his goodness. Some people attribute the deceived to the imperfection, fate or a continuous chain of events; it’s hard to believe God since he had leaded us to falsehoods.

Fourthly, Descartes gives the demon argument. Since the god is supremely good and he won’t deceive us, he supposed there is a malicious demon of the utmost power as God and cunning has employed all his energies in order to deceive me. We have nothing but the demon makes us falsely believing that we have all these things. Thus the only hope of the all-good’s God, which can makes us ensure something, has broken. There is nothing in the external world we can believe, or even we cannot believe whether the external world exists. In Descartes’ view, the possibility of demon is decisive to prove the universal of doubt.

  1. Are Descartes’ skeptical arguments convincing?

Up to now, Descartes had finished his arguments, which gives him a rational basis of universal skepticism. If we make an evaluation of his arguments, we can easily find some deficiencies. I can figure out two points of them.

Firstly, Descartes finished his argument appeal to the God and demon. But the existence and properties of the God and demon are seek for prove. So Descartes finished his arguments based on the unreliable evidences (or can say hypothesis). Obviously, they are not convincible, neither are they reliable in logical tests.

Secondly, the things that Descartes doubts, including those creations as he said, are merely refer to the sense perceptions in his mind. There is not a dividing line between the things in mind and those objective realities. The perceptions in minds may be incorrect or illusory, but the external world is objective existence. It is the basis and the guarantee to the truth our understanding. For example, the sun in external world is a huge celestial body, but the projection of the sun in our minds is tiny. We cannot deny its existence and properties because of the unrealistic size of the sun in mind, and it is easily to distinguish the difference of them by science principles. As a scientist, Descartes should fully understand these.

However, Descartes had figured out his aim is to prove the possibility and rationality of universal skepticism, and then “demolish everything completely and start again right from the foundations if I wanted to establish anything at all in the sciences that I was stable and likely to last” [3], which I think is a system of metaphysics. The eternal world, which he has admitted as a scientist, and the methods to understand the eternal world are can be only clarified in the proving of this metaphysics system. So, resorting to the relationship of the subjective understanding and the enteral world is unhelpful to prove the rationality and possibility of universal skepticism.

So, I think it is necessary to understand that the universal skepticism is not a purpose, but the method to eliminate faults and finally reach the truths. But, what undoubtful truth had Descartes reached by the universal skepticism?

In the despair of failing to find any bases to find rationale knowledge at the end of Meditation I, Descartes keep searching for foundation of knowledge and presents his Meditation II. He realizes that there are two beliefs he holds cannot be denied: I think and I exist. We cannot doubt because we have to be exist in order to think. Also thinking has all kinds of deviated forms. Under Descartes thought, we can argue that although we cannot be sure about we are seeing certain items through visions, we cannot deny that we seem to be seeing things, according to our mind. Such seemingly truth is infallible because it is the variation of “I think”. Accordingly, what our mind “sees” the world provide bases for us to describe the world, in other words, knowledge of the natural world. Thus, “I think, therefore I am.”


  1. Descartes, Rene. 1984. The Philosophical Writings VOLUME II: Meditations on First Philosophy. New York: Cambridge University Press.
  2. 周晓亮. 大家精要:笛卡儿. 昆明:云南教育出版社. 2009
  3. 冯俊. 开启理性之门:笛卡尔哲学研究. 北京 : 中国人民大学出版社, 2005

[1] Descartes: Meditations on First Philosophy, p17

[2] Descartes: Meditations on First Philosophy, p17

[3] Descartes: Meditations on First Philosophy, p17

本作品采用知识共享署名-非商业性使用-相同方式共享 2.5 中国大陆许可协议进行许可。


1 条评论。

  1. 12/8 飞了 « In Wandering - pingback on 2011/12/08 在 20:16


Trackbacks and Pingbacks: