Instead of rejecting this argument out of hand, as "language-lawyering," allow me to suggest a different approach. It sounds like you and I agree that Putnam's

Instead of rejecting this argument out of hand, as "language-lawyering," allow me to suggest a different approach. It sounds like you and I agree that Putnam's argument doesn't actually tell us that we are not brains in vats. I think Putnam would agree with us as well. So what's the real point? Any discourse about whether we are brains in vats is hopelessly defective. Even if we accidentally issued the right string of symbols, or made the right sequence of noises, our statements would be objectively meaningless, because they are not causally related to the phenomena they would otherwise describe. What's the use of this kind of thought? Here's a candidate: any philosophical debate that can be made the target of this pattern of argument is an argument that is not worth having. It cannot lead to real knowledge even if the disputants happen to arrive at what would be the right answer. This argument takes as a premise that the conclusion "I am a brain in a vat" is not causally related to the actual brain or the actual vat. This would seem to suggest, among other things, that there can be no concrete evidence for this claim--and Putnam is telling us that if we indulge in such a debate anyway we are not merely unlikely to hit upon the right answer, but that we are doomed to talk nonsense.