What Is Rene Descartes Evil Demon

Does Descartes’ “evil demon” thought experiment show that we cannot know anything about the external world?

Descartes’ ‘evil demon’ thought experiment was originally imagined by Rene Descartes in Meditations I. The thought experiment still remains relevant in the modern day, with the popularity of the ‘brain in a vat’ thought experiment and its numerous parallels in films such as the Matrix and Total Recall.

Descartes tries to deconstruct his preconceived beliefs about the world, to truly understand what we do and do not know. He begins by examining his senses. He realises that there are many times when our senses deceive us. Phantom pains, hallucination, all of these bring into question the reliability of the senses and thus the beliefs
‘Everything’, Descartes says, ‘that I accepted as being most true up to now I acquired from the senses or through the senses. However, I have occasionally found that they deceive me, and it is prudent never to trust those who have deceived us, even if only once’. The reason why this doubt is universal is that senses give no way to distinguish a true from a false perception. Descartes is not saying here that the senses are wrong, but simply that we cannot be certain that everything they tell us is correct.

Having realised that our senses deceive us and so we cannot trust them, Descartes immediately raises an objection: if it is reasonable to doubt what the senses tell us about those things that they perceive only weakly and faintly, is it also necessary to question the much more powerful and immediate perceptions, such as that of having a body and
It asks us to imagine there is a person who happens to believe precisely what you believe, undergoes experiences indistinguishable from your own, seems to recall and remember everything you recall and remember, and is disposed to reason in precisely the same way you reason. Imagine that this person is deceived by a Cartesian demon, but you are not. If the world around us really is as we perceive it for the most part, then many of your beliefs about the external world are knowledge. Since the counterpart is systematically deceived by the evil demon, his beliefs about the external world do not constitute knowledge. Furthermore, it seems that while you might think that your beliefs are produced by processes that can reliably lead you to the truth, the means by which your counterpart arrives at her beliefs are wholly unreliable. Since you can’t have a justified belief about something unless the means by which you arrive at that belief is reliable, it seems the view of many philosophers ought to say that your counterpart’s beliefs are not justified, and so are not knowledge. If your beliefs about the external world are induced by hallucinatory experiences, you do not have the right to believe what you do; rather, you only appear to have that right. This is strongly counterintuitive. If someone is identical to you in every way and believes exactly the same things as you,