Journal of Philosophy 107 (5):243-256 (2010)

Sherrilyn Roush
University of California, Los Angeles
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
Keywords Analytic Philosophy  Contemporary Philosophy
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ISBN(s) 0022-362X
DOI 10.5840/jphil2010107518
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References found in this work BETA

Knowledge and Its Limits.Timothy Williamson - 2000 - Philosophy 76 (297):460-464.
Epistemic Operators.Fred I. Dretske - 1970 - Journal of Philosophy 67 (24):1007-1023.
External World Skepticism.John Greco - 2007 - Philosophy Compass 2 (4):625–649.

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Citations of this work BETA

Questions, Topics and Restricted Closure.Peter Hawke - 2016 - Philosophical Studies 173 (10):2759-2784.
A Problem for the Closure Argument.Philip Atkins & Ian Nance - 2014 - International Journal for the Study of Skepticism 4 (1):36-49.
Sensitivity And Closure.Mark McBride - 2014 - Episteme 11 (2):181-197.

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