How (if at all) do you know that you are not a brain in a vat?

Résumé du document

Our whole life (attitudes, reactions, actions) is based on knowledge. Depending on our present state of knowledge, we react to different situations in different ways, give different answers to different questions. To do that, one has to know something. Even though we do not tend to question our knowledge in everyday life, it is interesting to do so in order to (ideally) find an answer to the sceptics who deny that knowledge exists, who assert that we cannot know anything for sure. In this paper, I will address the question: "How (if at all) do you know that you are not a brain in a vat? which is a question posed by the skeptics who intend to show that one cannot know the answer to it.

Extraits

[...] For a theory to let us know that we are BIVs, it would have to show that BIVs could not reflect on such question, nor understand it. If that were the case, then since we are reflecting on it we cannot be BIVs. Hilary Putnam did attempt to use that path by saying that set of mental events constitutes understanding'[11]. Here she means that even though a BIV might ‘see' a tree, it will not know that it is one because it is no linked to the external world, words and images have no intrinsic meaning, that is why the external world is needed. [...]

[...] It tells us that S's belief that it is not a BIV is caused by the exact fact that it is not a BIV. But we cannot say this condition to be fulfilled because, if S was a BIV, she would still believe she was not (it's one of the premises of the hypothesis). So S cannot know that is not a BIV. We might get round that problem if we succeed in proving that I can know that I am a BIV. [...]

[...] The 3rd one does not because if I was not not a BIV simpler said, if I was a BIV) then I would still believe that p. Therefore it cannot help us to know that we are not BIVs. His theory, however, can let us know other facts. Suppose S is ‘I' and p is am brushing my teeth. All four conditions are met, so you can be said to know that you are brushing you teeth. But, then, according to the principle of closure, if you know that p then you know that q are not a BIV' because p entails q. [...]

[...] But, the same day, there were lots of Diana look-alikes in the street to protest against monarchy and that fact was advertised in the newspapers. So if you had red the newspapers you would not believe just to have seen Diana, even though it really was her that you saw that day. Therefore it was not knowledge. Adam Morton, A guide through the theory of knowledge, 2nd edition, Oxford, Blackwell publishers p.123. See Dancy, Introduction to contemporary Epistemology, p.38. Hilary Putnam, ‘Brains in a Vat', in K. [...]

[...] theory of justification is internalist if and only if it requires that all the factors needed for a belief to be epistemologically justified for a given person be cognitively accessible to that person, internal to his cognitive perspective ; and externalist, if it allows that at least some of the justifying factors need not be thus accessible, so that they can be external to the believer's cognitive perspective, beyond his ken.' Dancy & Sosa A Companion to Epistemology, Cambridge Blackwell reference p.132. What I mean by conclusive here is to get an answer that assures us that we are not BIVs. [...]