Chalmers gave an argument that the brain in the VAT does not lead to skepticism (even if I am the brain in the VAT, I can also say "I have one hand is true") in his "The Matrix as Metaphysics"(for the “philosophy section” of the official Matrix website. It also appears in C.Grau,ed,Philosophers Explore the Matrix, Oxford University Press, 2005. ) ,meaningly ,we could infer the law even if we are living in a virtual world and other objections will also rise even in a picture of non-brain-in-a-vat. How about his argument?
Chalmers' point in "The Matrix as Metaphysics" is that the brain-in-a-vat hypothesis should be considered a metaphysical hypothesis rather than a skeptic's thought experiment.
Suppose we are in fact envatted brains. Envatted or not, we still live in a "real" world. Even if our reality is simulated, it still comes from somewhere, we still find ourselves living in it, and it still operates according to various laws. It's still real; it's simply a different kind of real than is commonly considered real (i.e. physical, material, etc.).
This is Chalmers' point. The question "Are we brains in vats?" should not be discussed in terms of being skeptical about "how real" the reality in which we find ourselves is; instead, it deserves to be treated as a discussion of the fundamental and metaphysical nature of the reality we find ourselves in.