Frederic Fitch and epistemic blindspotting
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1990
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Abstract
This thesis investigates the problem of epistemic blindspotting initiated by Frederic Fitch's Theorem 5 (FT5) which says: if there is some true proposition which nobody knows (or has known or will know) to be true, then there is a true proposition which nobody can know to be true. An epistemic blindspot is defined as a proposition which, though true, cannot be known (to be true).
Fitch did not consider the factors of time and agency in his proof, and he indicated that a more detailed treatment should take those factors seriously. This thesis first supplies that more detailed treatment by giving a complete version of the formal proof of FT5 with quantifiers over agents, time and eternal sentences. The thesis further strengthens Fitch's result by refuting the attempts of Schlesinger and Edgington to dissolve Fitch's result, and by showing that FT5 holds with the modal expression 'can' interpreted either as logical possibility or as ability. It shows that even the weakest classical modal system yields Fitch's result. It also proves a theorem which indicates that even some doxastic concepts generate potential epistemic blindspots.
With respect to the philosophical implications of Fitch's result, the thesis shows that for any true proposition, we cannot identify it as being an epistemic blindspot. This position was supported by proving the following two conclusions. First, for any true proposition, nobody is able to know that it is a true proposition which nobody is able to know to be true. Secondly, for any true proposition, it is logically impossible to know that it is a true proposition which it is logically impossible to know to be true. So even if there are epistemic blindspots we cannot locate them.
It is made clear that while FT5, together with the plausible assumption that there are unknown true propositions, establishes that it is possible that there are epistemic blindspots, it is also possible that there are no epistemic blindspots. This conclusion is based on the facts that FT5 does not prevent us from knowing true atomic propositions, and that FT5 does not prevent us from knowing a proposition of the form 'Kp', where 'p' is an atomic proposition. For all that FT5 shows, perhaps .every true proposition may be known at some time or other. Nevertheless, FT5 establishes a formal limit to human knowledge and helps us to understand some of our epistemic concepts.
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Bibliography: p. 162-173.
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Citation
Kang, O. J. (1990). Frederic Fitch and epistemic blindspotting (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/16285