It's all about the deep questions.
Skepticism – The Brain in the Vat Argument: Intro
My favorite debates in epistemology have always been the debates for and against skepticism, and the “brain in the vat” thought experiment has always been a classic in the field. Here, I will present the argument and give a few preliminary justifications. Later, another posts will consider the objections and counter-objections to the argument.
1. If one knows some fact about the external world, p, then one can or could know that he at least believes that p and, furthermore, that there is no evil scientist, a being other than himself, who is deceiving him into falsely believing that p.
2. In respect of anything which might be known or believed about the external world, say p, no one can our could know that he at least believes that p and that there is no evil scientist, a being other than himself, who is deceiving him into falsely believing that p.
3. In respect of anything which might be known or believed about the external world, say, that p, no one ever knows that p.
This premise relies on “the assumption of reasoning” or the fact that knowledge is closed under entailment. Basically, if one knows that p, and it is true that p entails q, then one can or could know that q. So, if someone knows some fact p, then that entails that he can or could know that he is not being falsely deceived into believing that p. Lastly, the first part of the “then” clause relies on the almost unanimously agreed fact that to know that p, it is necessary to believe that p. It is the second part of the “then” clause which cannot be satisfied. As a whole, I see this premise to really be uncontroversial. After all, how could it be false?
This comes to the classic “brain in the vat” scenario. Intuitively, one can never know that one is not a brain in a vat being poked by electrodes to falsely believe in various propositions. This premise has, however, been objected to, and we will look into those objections later. The first time I heard this premise though, I thought it was pretty obvious.