The argument that has inspired much of the recent discussion of the logical relationship between these views is found in Putnam : If externalism is true, then if S were a brain in a vat, S’s utterances of the sentence “I am a brain in a vat” would not express the proposition that S is a brain in a vat. S’s use of the words “brain” and “vat” would not refer to a real brain or vat, just as, in a (...) Twin Earth-style thought experiment, the Twin Earthling cannot refer to water with his use of the term “water.” If we accept that generally we have knowledge of the contents of our utterances, then, if S knows that her utterances of “brain” and “vat” mean brain and vat, it will be possible for S to know that she is not a brain in a vat. For if S has authority with respect to the contents of her utterances, then she can know that her utterance, “I am not a brain in a vat,” refers to brains and vats. On externalism, since S would not refer to brains and vats if she were a brain in a vat, she could know by mere introspection that she is not a brain in a vat. In fact, S can come to know many arbitrary propositions about the external world simply by attending to the contents of her thoughts. For if externalism is true, she can argue, then certain empirical conditions must be satisfied if she is even to have the thoughts about the external world that she does; since she knows what she is thinking, she knows these empirical conditions are satisfied. Thus, if S knows that she is thinking about brains and vats, then she can know that she is not a brain in a vat ; for if she was a BIV, then she would not be thinking about brains and vats, but instead about electrical impulses or some such thing. The standard BIV argument against scepticism, therefore, cannot be correct. This line of argument can then be used to conclude more generally that scepticism is false; for the argument can be run with virtually any utterance or thought with empirical content. If S knows that she is thinking about trees, for example, then she can know that there are trees. (shrink)

The argument that has inspired much of the recent discussion of the logical relationship between these views is found in Putnam : If externalism is true, then if S were a brain in a vat, S’s utterances of the sentence “I am a brain in a vat” would not express the proposition that S is a brain in a vat. S’s use of the words “brain” and “vat” would not refer to a real brain or vat, just as, in a (...) Twin Earth-style thought experiment, the Twin Earthling cannot refer to water with his use of the term “water.” If we accept that generally we have knowledge of the contents of our utterances, then, if S knows that her utterances of “brain” and “vat” mean brain and vat, it will be possible for S to know that she is not a brain in a vat. For if S has authority with respect to the contents of her utterances, then she can know that her utterance, “I am not a brain in a vat,” refers to brains and vats. On externalism, since S would not refer to brains and vats if she were a brain in a vat, she could know by mere introspection that she is not a brain in a vat. In fact, S can come to know many arbitrary propositions about the external world simply by attending to the contents of her thoughts. For if externalism is true, she can argue, then certain empirical conditions must be satisfied if she is even to have the thoughts about the external world that she does; since she knows what she is thinking, she knows these empirical conditions are satisfied. Thus, if S knows that she is thinking about brains and vats, then she can know that she is not a brain in a vat ; for if she was a BIV, then she would not be thinking about brains and vats, but instead about electrical impulses or some such thing. The standard BIV argument against scepticism, therefore, cannot be correct. This line of argument can then be used to conclude more generally that scepticism is false; for the argument can be run with virtually any utterance or thought with empirical content. If S knows that she is thinking about trees, for example, then she can know that there are trees. (shrink)

1. Metaphysical Realists have traditionally relied upon the skeptic to give substance to the idea that truth is, in the words of Hilary Putnam, 'radically non-episternic,’ forever outstripping, in principle at least, the reach of justification. What better model of truth so conceived, after all, than the skeptic's contention that even our firmest convictions might be mistaken in that we might be the victims of demonic deception or the machinations of an evil scientist? But the availability of this favorite model (...) of Realist truth, encapsulated in the claim that we might be ‘brains in a vat,’ has been called into question by Putnam in the opening chapter of Reason, Truth, and History. Putnam contends that, if we grant the Realist notion of truth, as referentially mediated correspondence to THE WORLD, then, given certain plausible constraints on reference, we can know that we are not brains in a vat. (shrink)

1. Metaphysical Realists have traditionally relied upon the skeptic to give substance to the idea that truth is, in the words of Hilary Putnam, 'radically non-episternic,’ forever outstripping, in principle at least, the reach of justification. What better model of truth so conceived, after all, than the skeptic's contention that even our firmest convictions might be mistaken in that we might be the victims of demonic deception or the machinations of an evil scientist? But the availability of this favorite model (...) of Realist truth, encapsulated in the claim that we might be ‘brains in avat,’has been called into question by Putnam in the opening chapter ofReason, Truth, and History.Putnam contends that, if we grant the Realist notion of truth, as referentially mediated correspondence to THE WORLD, then, given certain plausible constraints on reference, we can know that we arenotbrains in a vat. (shrink)

SummaryA familiar sort of argument for skepticism about the external world appeals to the evidential similarity between what is presumed to be the normal case and the case where one is a brain in a vat. An argument from Putnam has been taken by many to provide an a priori refutation of this sort of skeptical argument. The question I propose to address in this paper is whether Putnam's argument affords us an a priori refutation of skeptical arguments that appeal (...) to the claim that one does not know that one is not a BIV. I will develop a negative answer to this question along two related fronts. Along the first front I defend against new criticisms the common position that the externalism on which Putnam's argument is based entails skepticism about the meanings of sentences in our language and the contents of our thoughts. I do not take this to be a refutation of externalism or externalist arguments; rather, I see this as a motivation to locate the difficulty with arguments for externalism. But if externalism is abandoned, of course, the anti‐skeptical argument it has widely been taken to support must be abandoned along with it. I will argue, however, that this is not a significant loss, because along a second front I will argue that externalism cannot be given a priori justification; it is therefore ill‐suited to ground an a priori refutation of BIV skepticism anyway. (shrink)