You know that you have hands only if you can discriminate between actually having hands and the alternative of being a handless brain-in-a-vat.

Next, we will examine various responses to the BKCA argument. According to the first, we can see that (C2) is false if we distinguish between relevant and irrelevant alternatives. An alternative to a proposition p is any proposition that is incompatible with p. Your having hands and your being a BIV are alternatives: if the former is true, the latter is false, and vice versa. According to the thought that motivates the second premise of the BIV argument, you know that you have hands only if