Rational self-doubt and the failure of closure
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Closure for justification is the claim that thinkers are justified in believing the logical consequences of their justified beliefs, at least when those consequences are competently deduced. Many have found this principle to be very plausible. Even more attractive is the special case of Closure known as Single-Premise Closure. In this paper, I present a challenge to Single-Premise Closure. The challenge is based on the phenomenon of rational self-doubt—it can be rational to be less than fully confident in one’s beliefs and patterns of reasoning. In rough outline, the argument is as follows: Consider a thinker who deduces a conclusion from a justified initial premise via an incredibly long sequence of simple competent deductions. Surely, such a thinker should suspect that he has made a mistake somewhere. And surely, given this, he should not believe the conclusion of the deduction even though he has a justified belief in the initial premise.
KeywordsSingle-premise closure Justification Competent deduction Deductive inference Long sequence argument Rational self-doubt
Earlier versions of this paper were presented at the Basic Knowledge III workshop at the University of St. Andrews, a workshop on epistemology at the University of Geneva, the Theoretical Philosophy forum at Eötvös University, departmental colloquia at the University of Connecticut and at Princeton University, and the Epistemology Reading Group at MIT. I would like to thank the audiences at these events for their questions and comments. I would also like to thank Maria Lasonen Aarnio, Paul Boghossian, David Christensen, Stew Cohen, Dylan Dodd, Adam Elga, David Estlund, Hartry Field, Phil Galligan, Michael Heumer, Chris Hill, Ram Neta, Stephen Read, Gideon Rosen, Nico Silins, Paul Silva, Ralph Wedgwood, Tim Williamson, and Zsofia Zvolensky for helpful discussions at various stages of this project.
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