Fitch’s Paradox shows that if every truth is knowable, then every truth is known. Standard diagnoses identify the factivity/negative infallibility of the knowledge operator and Moorean contradictions as the root source of the result. This paper generalises Fitch’s result to show that such diagnoses are mistaken. In place of factivity/negative infallibility, the weaker assumption of any ‘level-bridging principle’ suffices. A consequence is that the result holds for some logics in which the “Moorean contradiction” commonly thought to underlie the result is (...) in fact consistent. This generalised result improves on the current understanding of Fitch’s result and widens the range of modalities of philosophical interest to which the result might be fruitfully applied. Along the way, we also consider a semantic explanation for Fitch’s result which answers a challenge raised by Kvanvig. (shrink)

The beliefs involved in the placebo effect are often assumed to be self-fulfilling, that is, the truth of these beliefs would merely require the patient to hold them. Such a view is commonly shared in epistemology. Many epistemologists focused, in fact, on the self-fulfilling nature of these beliefs, which have been investigated because they raise some important counterexamples to Nozick’s “tracking theory of knowledge.” We challenge the self-fulfilling nature of placebo-based beliefs in multi-agent contexts, analyzing their deep epistemological nature and (...) the role of higher-order beliefs involved in the placebo effect. (shrink)

An analysis of Moore's paradox is given in doxastic logic. Logics arising from formalizations of various introspective principles are compared; one logic, K5c, emerges as privileged in the sense that it is the weakest to avoid Moorean belief. Moreover it has other attractive properties, one of which is that it can be justified solely in terms of avoiding false belief. Introspection is therefore revealed as less relevant to the Moorean problem than first appears.

An alternative view to the traditionally held view that schizophrenia is characterised by severely disordered cognition is presented. It is possible that apparently self- contradictory expressions of schizophrenics are well-formed communicative expressions of highly ordered cognitive systems. Building on the premise that behavior is in general communicative, and using Godel’s Incompleteness Theorem from logic as a model, it is shown that the most characteristic symptoms of schizophrenia may indicate truths that cannot be derived within highly ordered cognitive systems.

Crispin Wright tried to refute classical 'Cartesian' skepticism contending that its core argument is extendible to a reductio ad absurdum (_Mind<D>, 100, 87-116, 1991). We show both that Wright is mistaken and that his mistakes are philosophically illuminating. Wright's 'best version' of skepticism turns on a concept of warranted belief. By his definition, many of our well-founded beliefs about the external world and mathematics would not be warranted. Wright's position worsens if we take 'warranted belief' to be implicitly defined by (...) the general principles governing it. Those principles are inconsistent, as shown by a variant of Godel's argument. Thus the inconsistency Wright found has nothing to do with the special premises of Cartesian skepticism, but is embedded in his own conceptual apparatus. Lastly, we show how a Cartesian skeptic could avoid Wright's critique by reconstructing a skeptical argument that does not use the claims Wright ultimately finds objectionable. (shrink)

In this paper we use proof-theoretic methods, specifically sequent calculi, admissibility of cut within them and the resultant subformula property, to examine a range of philosophically-motivated deontic logics. We show that for all of those logics it is a (meta)theorem that the Special Hume Thesis holds, namely that no purely normative conclusion follows non-trivially from purely descriptive premises (nor vice versa). In addition to its interest on its own, this also illustrates one way in which proof theory sheds light on (...) philosophically substantial questions. (shrink)

Smullyan wrote his famous book of puzzles before the boom in automated theorem proving and he solved the puzzles by hand. Hence it is interesting to investigate whether all the puzzles can be solved with one method or not. The paper shows how this can be done with analytic tableaux.