If the contents of our thoughts are partly determined by facts outside our heads, can we still know those contents directly, without investigating our environment? What if we were surreptitiously switched to Twin-Earth? Would we know the contents of our thoughts under these unusual circumstances? By looking carefully at what determines the content of a second-order thought, a candidate for self-knowledge, the paper argues that we can know the contents of our thoughts directly, even after being switched. Learning about the (...) switch, however, does raise some interesting difficulties. (shrink)

Psychological externalism is the thesis that the contents of many of a person's propositional mental states are determined in part by relations he bears to his natural and social environment. This thesis has recently been thrust into prominence in the philosophy of mind by a series of thought experiments due to Hilary Putnam and Tyler Burge. Externalism is a metaphysical thesis, but in this work I investigate its implications for the epistemology of the mental. I am primarily concerned with the (...) question whether externalism undermines the idea that a person typically knows the contents of her own thoughts, beliefs, and other propositional attitudes directly and authoritatively. I criticize arguments that have been advanced on behalf of a positive answer to this question, and argue that they rest on a faulty conception of the nature of first person authority, one which likens our access to our own minds to perception. An account of the basis of first person authority is sketched that locates our epistemic right to our self-ascriptions of propositional attitude not in our ability to discriminate among the various thought contents we might be thinking, but rather in our ability to express our thoughts, and to think with them in accordance with the norms of rationality. I consider also the question whether first person authority and externalism jointly make possible a refutation of certain forms of global skepticism, as has been famously argued by Putnam. I argue that Putnam's attempted refutation fails, because the crucial externalist claims that drive it are not knowable a priori. (shrink)

Using a quantified propositional logic involving the operators it is known that and it is possible to know that, we formalize various interesting philosophical claims involved in the realism debate. We set out inferential rules for the epistemic modalities, ranging from ones that are obviously analytic, to ones that are epistemologically more substantive or even controversial. Then we investigate various aporias for the realism debate. These are constructively inconsistent triads of claims from our list: a claim expressing some sort of (...) common ground in the debate; a characteristically anti-realist thesis about truth and knowability; and a characteristically realist thesis about determinacy of truth value. Various patterns of reductio proof for these inconsistent triads are generated, so as to display their variety. The reductio proofs use only the inferential rules set out earlier. The philosophical utility of each aporia for the anti-realist is then assessed. This involves consideration of the acceptability of the premiss expressing common ground; the strength and plausibility of the anti-realist premiss; the strength of the realist premiss that is the ultimate target of the reductio; and the analytic status of the inferential rules applied within the proof. (shrink)

Tr(A) iff ‡K(A) To remedy the error, Dummett’s proposes the following inductive characterization of truth: (i) Tr(A) iff ‡K(A), if A is a basic statement; (ii) Tr(A and B) iff Tr(A) & Tr(B); (iii) Tr(A or B) iff Tr(A) v Tr(B); (iv) Tr(if A, then B) iff (Tr(A) Æ Tr(B)); (v) Tr(it is not the case that A) iff ¬Tr(A), where the logical constant on the right-hand side of each biconditional clause is understood as subject to the laws of intuitionistic (...) logic.2 The only other principle in play in Dummett’s discussion is (+) A iff Tr(A), which, as he notes, the anti-realist is likely to accept. (shrink)