Brain in a vat

Chapter 4 is about truth. The first section discusses how truth should be understood if we have a conceptual scheme in place. However, not all conceptual schemes are equally good. The second section spells out how conceptual schemes can be evaluated. The final section uses Putnam s brains in a vat argument to show that internal realism has a better to chance to avoid skepticism than internal realism. 

If we disregard the parenthetical remarks, (PI) is but a tautology. The parenthetical remarks have been justified in the previous discussion. (P2) is the contraposition of the T-equivalence involving the sentence We are brains in a vat in classical logic, where p is not true is equivalent with p is false . 

Is there a way to overcome this difficulty The way to get rid of this kind of inconsistency is to eliminate the self-reference. The sentence The sentence mentioned in the previous paragraph between saying and or is not in English is not inconsistent. Similarly, Bill is not speaking English now is not inconsistent. The reason why the objection turned out to be inconsistent is that we asserted of ourselves that we are brains in a vat. To avoid the inconsistency, we have to drop the first person idiom. We should suppose that they are brains in a vat. 

BP1) They are either brains in a vat (speaking vat-English) or they are not brains in a vat (speaking English). 

But is this a fair objection One may argue that it is not. It challenges Brutnam to prove an English sentence, a feat Brutnam cannot possibly accomplish, since he does not and cannot speak English. It follows from his existential condition that English is not available to him. A brain in a vat can speak only some kind of vat-language. The objector may answer that this is just the point. Skepticism cannot be refuted, because the skeptical scenarios are loaded. To refute skepticism, you need a... 

This is a simplified version of Anthony Brueckner s ( Putnam s Model-Theoretic ) reconstruction of the argument. Most other reconstructions consider only one horn of the dilemma, the first disjunct of (PI), (P3) and (C). The various reconstructions in the literature differ only in small details which are not relevant from the present point of view. I could have used almost any one of them to make my point, but Brueckner s reconstruction makes this especially easy. For further details see Harrison ( Putnam on Brains ), Casati and Dokic ( Brains in a Vat ), David ( Neither Mentioning ), Tymoczko( In Defense , Brains Don t Lie ), Tichy ( Putnam on Brains ), Farrell ( Putnam on the Vat-People ), Kinghon ( External World ), Van Kirk ( Kant s Reply ), Heil ( Epistemic Route ), Sacks (The World, 56-76)), Nagel (The View From Nowhere, 71-4), Dell Utri ( The Case of the Brains ), Collier ( Could I... 

Brown, Curtis. Internal Realism Transcendental Idealism In French, Uehling, Wettstein, 145-155. Brueckner, Anthony L. Brains in a Vat. The Journal of Philosophy 83 (1986) 148-167. 

Casati, Roberto and Dokic, Jerome. Brains in a Vat, Language, Metalanguage , Analysis 51 (1991) 91-93. 

Collier, John D. Could I Conceive Being a Brain in a Vat Australasian Journal of Philosophy 68... 

David, Marian. Neither Mentioning Brains in a Vat nor Mentioning Brains in a Vat Will Prove that We Are Not Brains in a Vat. Philosophy and Phenomenological Research 51 (1991) 891-896. 

A third reason is provided by the observation that I myself might conceivably be a brain in a vat, wired to a computer that is supplying me with inputs. This being so, how things are outside the brain does not really matter to phenomenology. If the brain states are the same, the phenomenology must be the same, whatever the external causes (Horgan and Tiensen, 2002). 

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