A well known skeptical paradox rests on the claim that we lack warrant to believe that we are not brains in a vat (BIVs). The argument for that claim is the apparent impossibility of any evidence or argument that we are not BIVs. Many contemporary philosophers resist this argument by insisting that we have a sort of warrant for believing that we are not BIVs that does not require having any evidence or argument. I call this view ‘New Rationalism’. I (...) argue that New Rationalists are committed to there being some evidence or argument for believing that we are not BIVs anyway. Therefore, New Rationalism, since its appeal is that it purportedly avoids the problematic commitment to such evidence or argument, undermines its own appeal. We cannot avoid the difficult work of coming up with evidence or argument by positing some permissive sort of warrant. (shrink)

This is a response to a recent Philosophical Studies article by Bredo Johnsen, in which he makes a number of criticisms of Putnamian anti-skeptical arguments.

J.D. Collier sees Putnam as arguing (in the 'Brains in a Vat' chapter of [4]) that metaphysical realism is false.' He sees the argument as proceeding from the background assumption that metaphysical realism has the consequence that truth is 'radically non-epistemic', so that 'an [epistemically] ideal theory could be radically wrong about the world' [3, p. 413]. But, according to Collier, Putnam argues that 'an ideal theory satisfying all of our methodological and theoretical constraints cannot be false' [3, p. 413]. (...) Collier attempts to defend metaphysical realism against this Putnamian attack by distinguishing 'between our ability to state a theory and our ability to conceive its possibility' [3, p. 413]. I will show that this defence is unsuccessful. (shrink)

Massimo Dell'Utri (1990) provides a reconstruction of Hilary Putnam's argument (1981, chapter 1) to show that the hypothesis that we are brains in a vat is self-refuting. I will explain why the argument Dell'Utri offers us is, on the face of it, quite problematic. Then I will provide a way out of the difficulty.

In chapter 1 of Reason, Truth, and History, Hilary Putnam argues from some plausible assumptions about the nature of reference to the conclusion that it is not possible that all sentient creatures are brains in a vat. If this argument is successful, it seemingly refutes an updated form of Cartesian skepticism concerning knowledge of physical objects. In this paper, I will state what I take to be the most promising interpretation of Putnam's argument. My reconstructed argument differs from an argument (...) strongly suggested by Putnam's text. I will show that the latter argument obviously does not work. The more promising argument which I reconstruct on behalf of Putnam raises some interesting questions about the relation between the contents of one's beliefs and one's environment and about how this relation affects the evaluation of anti-skeptical arguments. I conclude that my reconstructed argument ultimately fails as a response to Cartesian skepticism: the argument engenders a skepticism about knowledge of meaning, or propositional content, which undercuts its anti-skeptical force. (shrink)

The Matrix presents a version of an old philosophical fable: the brain in a vat. A disembodied brain is floating in a vat, inside a scientist’s laboratory. The scientist has arranged that the brain will be stimulated with the same sort of inputs that a normal embodied brain receives. To do this, the brain is connected to a giant computer simulation of a world. The simulation determines which inputs the brain receives. When the brain produces outputs, these are fed back (...) into the simulation. The internal state of the brain is just like that of a normal brain, despite the fact that it lacks a body. From the brain’s point of view, things seem very much as they seem to you and me. (shrink)

In Reason, Truth, and History Hilary Putnam has presented an anti-skeptical argument purporting to prove that we are not brains in a vat. How exactly the argument goes is somewhat controversial. A number of competing "recon¬structions" have been proposed. They suffer from a defect which they share with what seems to be Putnam's own version of the argument. In this paper, I examine a very simple and rather natural reconstruction of the argument, one that does not employ any premises in (...) which a sentence, viz. the sentence 'I am a brain in a vat', is mentioned rather than used. In this respect my version of the argument is importantly different from what appears to be Putnam's own version. (shrink)

A few years back, I participated in the Spindell Conference in Memphis, and gave a paper, “How Can We Know That We’re Not Brains in Vats?” (available on-line at: http://pantheon.yale.edu/~kd47/Spindell.htm). The bulk of that paper concerned responses to skepticism. I pursued an unusually radical criticism of the often-criticized “Putnam-style” responses to skepticism. To put it rather enigmatically, I argued that such responses don’t work even if they work! And I compared such responses with the type of response I favor – (...) the “contextualist Moorean” response – to show how these latter responses are of a type that avoids the radical problems that plague Putnam-style responses. But in the final section of the paper, I turned briefly to a different, though related, issue, presenting my proposed solution to what’s often called the “McKinsey problem.”. (shrink)

This should be fairly close to the text of this paper as it appears in The Southern Journal of Philosophy 38 (2000), Spindel Conference Supplement: 121-148.

One of the advantages of classical foundationalism was that it was thought to provide a refutation of skeptical worries, which raise the specter that our beliefs might be extensively mistaken. The most extreme versions of these worries are expressed in familiar thought experiments such as the brain-in-a-vat hypothesis, which imagines a world in which, unbeknownst to you, your brain is in a vat hooked up to equipment programmed to provide it with precisely the same visual, auditory, tactile, and other sensory (...) inputs that you have in this world. As a result, your opinions about your immediate environment are the same as they are in this world. You have the same beliefs about your recent activities, your current physical appearance, your present job, and so on, but in fact you are a brain in a vat tucked away in a corner of a laboratory. Thus, in the brain-in-a-vat world, your beliefs about these everyday matters are mistaken, and mistaken not just in detail, but deeply mistaken. (shrink)

Recent literature in epistemology has focused on the following argument for skepticism (SA): I know that I have two hands only if I know that I am not a handless brain in a vat. But I don't know I am not a handless brain in a vat. Therefore, I don't know that I have two hands. Part I of this article reviews two responses to skepticism that emerged in the 1980s and 1990s: sensitivity theories and attributor contextualism. Part II considers (...) the more recent ‘neo-Moorean’ response to skepticism and its development in ‘safety’ theories of knowledge. Part III argues that the skeptical argument set out in SA is not of central importance. Specifically, SA is parasitic on skeptical reasoning that is more powerful and more fundamental than that displayed by SA itself. Finally, Part IV reviews a Pyrrhonian argument for skepticism that is not well captured by SA, and considers a promising strategy for responding to it. (shrink)

Zhuangzi’s Butterfly Dream story can be read as a skeptical response to the Cartesian Cogito, ergo sum solution, for it presents I exist as fundamentally unprovable, on the grounds that the notion about “I” that it is guaranteed to refer to something existing, which Descartes seems to assume, is unwarranted. The modern anti-skepticism of Hilary Putnam employs a different strategy, which seeks to derive the existence of the world not from some “indubitable” truth such as the existence of myself , (...) but from the meaning of some particular assertion I make. In this paper, I argue, however, that Putnam’s argument fails to deliver on the promise of showing the self-refuting nature of the skeptical hypothesis, as it relies on a double use of “I”, a fallacy of equivocation, reflecting an unsolved tension between the argument’s general premise, which is rather Zhuangzian in spirit, and his unwitting adoption of that unwarranted notion about “I”. I try to show further that the skepticism in Zhuangzi’s Butterfly Dream not only can be used to refute the proofs of the existence of the empirical I , but also is effective against accounts concerning the existence of the transcendental I. (shrink)

The brain-in-a-vat argument for skepticism is best formulated, not using the closure principle, but using the "Preference Principle," which states that in order to be justified in believing H on the basis of E, one must have grounds for preferring H over each alternative explanation of E. When the argument is formulated this way, Dretske's and Klein's responses to it fail. However, the strengthened argument can be refuted using a direct realist account of perception. For the direct realist, refuting the (...) BIV scenario is not a precondition on knowledge of the external world, and only the direct realist can give a non-circular account of how we know we're not brains in vats. (shrink)

Hillary Putnam has famously argued that we can know that we are not brains in a vat because the hypothesis that we are is self-refuting. While Putnam's argument has generated interest primarily as a novel response to skepticism, his original use of the brain in a vat scenario was meant to illustrate a point about the "mind/world relationship." In particular, he intended it to be part of an argument against the coherence of metaphysical realism, and thus to be part of (...) a defense of his conception of truth as idealized rational acceptability. Putnam's conclusions about the scenario are, however, actually out of line with central and plausible aspects of his own account of the relationship between our minds and the world. Reflections on semantics give us no compelling reason to suppose that claims like "I am a brain in a vat" could not turn out to be true. (shrink)

'If a person can think of an F, then that person has come into causal contact with an F in the right way' is a premise in an obvious reconstruction of Putnam's argument that we are not brains in vats. 'If a person can think of an F, then that person has come into causal contact with an F or with something at least as good as an F' is the only controversial premise in Descartes' argument for the existence of (...) God. Putnam's principle entails Descartes', which suggests that we should enquire after better versions of Putnam's proof. I present three variations and conclude that Putnam's semantic theory does not have anti-sceptical consequences. In contrast, given Descartes' cognitive situation, he was perfectly justified in accepting the soundness of his argument for the existence of God. (shrink)

Hilary Putnam has offered two arguments to show that we cannotbe brains in a vat, and one to show that our cognitive situationcannot be fully analogous to that of brains in a vat. The latterand one of the former are irreparably flawed by misapplicationsof, or mistaken inferences from, his semantic externalism; thethird yields only a simple logical truth. The metaphysical realismthat is Putnams ultimate target is perfectly consistent withsemantic externalism.

Abstract: Radical sceptical possibilities challenge the anti-realist view that truth consists in ideal rational acceptability. Putnam, as part of his defence of an anti-realist view, subjected the case of the brain in a vat to a semantic externalist treatment, which aimed to maintain the desired connection between truth and ideal rational acceptability. It is argued here that self-consciousness poses special problems for this externalist strategy. It is shown how, on a standard model of first-person reference, Putnam's brain in a vat (...) will be mistaken in its rational self-ascription of externalist predicates. The natural response, which employs an alternative model of first-person reference, is shown to have the equally realist consequence that there are enquiry-transcendent truths about the self. (shrink)

The most convincing – and shortest – version of Putnam''s argument against thepossibility of our eternal envattment is due toCrispin Wright (1994). It avoids most of themisunderstandings that have been elicited byPutnam''s original presentation of the argumentin Reason, Truth and History (1981).But it is still open to the charge ofquestion-begging. True enough, the premisses ofthe argument (disquotation and externalism) canbe formulated and defended without presupposingexternal objects whose existence appearsdoubtful in the light of the very skepticalscenario which Putnam wants to repudiate.However, (...) the argument is only valid if we add anextra premiss as to the existence of some external objects. In order to avoidcircularity, we should run the argument withexternal objects which must exist even if we arebrains in a vat, e.g. with computers rather thanwith trees. As long as the skeptic is engaged ina discussion of the brain-in-a-vat scenario, sheshould neither deny the existence of computersnor the existence of causal relations; for ifshe does, she is in fact denying that we arebrains in a vat. (shrink)

This paper surveys attempts in the recent literature to offer a modal condition on knowledge as a way of resolving the problem of scepticism. In particular, safety-based and sensitivity-based theories of knowledge are considered in detail, along with the anti-sceptical prospects of an explicitly anti-luck epistemology.

Hilary Putnam deals in this book with some of the most fundamental persistent problems in philosophy: the nature of truth, knowledge and rationality. His aim is to break down the fixed categories of thought which have always appeared to define and constrain the permissible solutions to these problems.

In this paper we offer an exegesis of Hilary Putnam’s classic argument against the brain-in-avat hypothesis offered in his Reason, truth and history (1981). In it, Putnam argues that we cannot be brains in a vat because the semantics of the situation make it incoherent for anyone to wonder whether they are a brain a vat. Putnam’s argument is that in order for ‘I am a brain in a vat’ to be true, the person uttering it would have to be (...) able to refer successfully to those things: the vat, and the envatted brain. Putnam thinks that reference can’t be secured without relevant kinds of causal relations, which, if envatted, the brain would lack, and so, it fails to be able to meaningfully utter ‘I am a brain in a vat’. We consider the implications of Putnam’s arguments for the traditional sceptic. In conclusion, we discuss the role of Putnam’s arguments against the brain in a vat hypothesis in his larger defense of his own internal realism against metaphysical realism. (shrink)

I use some ideas of Keith DeRose's to develop an (invariantist!) account of why sceptical reasoning doesn't show that I don't know that I'm not a brain in a vat. I argue that knowledge is subject to the risk-of-error constraint: a true belief won’t have the status of knowledge if there is a substantial risk of the belief being in error that hasn’t been brought under control. When a substantial risk of error is present (i.e. beliefs in propositions that are (...) false in nearby worlds), satisfying the constraint requires bringing the risk under control. This is achieved either by sensitivity, i.e. you wouldn’t have the belief if it were false, or by identifying evidence for the proposition. However, when the risk of error is not substantial (i.e. beliefs in propositions that are not false in nearby worlds), the constraint is satisfied by default. My belief that I am not a brain in a vat is insensitive and I have no evidence for it, but since it is not false in nearby worlds, it satisfies the constraint by default. (shrink)