I have always considered that the two questions respecting God and the Soul were the chief of those that ought to be demonstrated by philosophical rather than ...

This paper addresses a problem about epistemic warrant. The problem is posed by philosophical arguments for externalism about the contents of thoughts, and similarly by philosophical arguments for architecturalism about thinking, when these arguments are put together with a thesis of first person authority. In each case, first personal knowledge about our thoughts plus the kind of knowledge that is provided by a philosophical argument seem, together, to open an unacceptably ‘non-empirical’ route to knowledge of empirical facts. Furthermore, this unwelcome (...) prospect of transferring a ‘non-empirical’ warrant from premises about our own mental states and about philosophical theory to a conclusion about external environment or internal architecture seems to depend upon little more than the possibility of knowledge by inference. (The use of the scare-quoted term ‘non-empirical’ is explained a couple of paragraphs further on.). (shrink)

In this paper, I will clarify Jonathan Schaffer's; debasing scepticism, highlighting its logical structure. 1 In many current discussions of scepticism, its scope is limited to propositions about the external world which, if known at all, are known a posteriori. The standard sceptical set-up goes as follows. The sceptic specifies a sceptical hypothesis, or counterpossibility, that is incompatible with the external-world propositions that I claim to know. The hypothesis – e.g. that I am a brain in a vat – is (...) claimed by the sceptic to be within the realm of metaphysical possibility. The sceptical argument, in a nutshell, runs as follows. Choose some external-world proposition that I claim to know, say H = I have hands. By the principle that knowledge is closed under known entailment, if I know H, then I know ∼SK = I am not a handless brain in a vat. My evidence does not enable me to know ∼SK. Hence I …. (shrink)

This article is a response to an important objection that Sherrilyn Roush has made to the standard closure-based argument for skepticism, an argument that has been studied over the past couple of decades. If Roush's objection is on the mark, then this would be a quite significant finding. We argue that her objection fails.

The Neo-Moorean Deduction (I have a hand, so I am not a brain-in-a-vat) and the Zebra Deduction (the creature is a zebra, so isn’t a cleverly disguised mule) are notorious. Crispin Wright, Martin Davies, Fred Dretske, and Brian McLaughlin, among others, argue that these deductions are instances of transmission failure. That is, they argue that these deductions cannot transmit justification to their conclusions. I contend, however, that the notoriety of these deductions is undeserved. My strategy is to clarify, attack, defend, (...) and apply. I clarify what transmission and transmission failure really are, thereby exposing two questionable but quotidian assumptions. I attack existing views of transmission failure, especially those of Crispin Wright. I defend a permissive view of transmission failure, one which holds that deductions of a certain kind fail to transmit only because of premise circularity. Finally, I apply this account to the Neo-Moorean and Zebra Deductions and show that, given my permissive view, these deductions transmit in an intuitively acceptable way—at least if either a certain type of circularity is benign or a certain view of perceptual justification is false. (shrink)

I set out the standard view about alleged examples of failure of transmission of warrant, respond to two cases for the view, and argue that the view is false. The first argument for the view neglects the distinction between believing a proposition on the basis of a justification and merely having a justification to believe a proposition. The second argument for the view neglects the position that one's justification for believing a conclusion can be one's premise for the conclusion, rather (...) than simply one's justification for the premise. Finally, the view is false since it is inconsistent with the closure of knowledge as closure is properly understood. (shrink)

What knowledge is imperilled by sceptical doubt? That is, what range of beliefs may be called into doubt by sceptical nightmares like the Cartesian demon hypothesis? It is generally thought that demons have limited powers, perhaps only threatening a posteriori knowledge of the external world, but at any rate not threatening principles like the cogito. I will argue that there is a demon – the debasing demon – with unlimited powers, which threatens universal doubt. Rather than deceiving us with falsities, (...) the debasing demon would allow us true beliefs, but only as guesses. (shrink)

It is received wisdom that the skeptic has a devastating line of argument in the following. You probably think, he says, that you know that you have hands. But if you knew that you had hands, then you would also know that you were not a brain in a vat, a brain suspended in fluid with electrodes feeding you perfectly coordinated impressions that are generated by a supercomputer, of a world that looks and moves just like this one. You would (...) know you weren’t in this state if you knew you had hands, since having hands implies you are no brain in a vat. You obviously don’t know you’re not a brain in a vat, though—you have no evidence that would distinguish that state from the normal one you think you’re in. Therefore, by modus tollens, you don’t know you have hands. At least, the skeptic has a devastating argument, it is thought, if we grant him closure of knowledge under known implication, which many of us are inclined to do: roughly, if you know p, and you know that p implies q, then you know q. (shrink)