 Consider a science fiction scenario concerning a human brain that is removed from its skull, kept alive in a vat of nutrient fluid, and electrochemically stimulated to have precisely the same total series of experiences that you have had. Call such a brain a “BIV”: a BIV would believe everything that you believe, and would (it is often thought) be justified in believing those things to precisely the same extent that you are justified in believing them. Therefore, justification is determined solely by those internal factors that you and your envatted brain doppelganger share. This view is what has come to be called “internalism” about  justification.[29]