Abstract
In [1], D. W. Hart and C. Mcginn considered two logics A1 and A2. These logics embody part of a tradition about a priori knowledge and necessity. They proved that A2 is a conservative extension of a well-known modal logic S5 but left the problem whether A1 is a conservative extension of S4 open. In this note, we shall show that A1 is not a conservative extension of S4 but of S5, and also correct an inadequate proof.
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References
W. D.Hart and C.Mcginn, ‘Knowledge and Necessity’, Jour. of Phil. Logic, 5 (1976), 205–208.
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Kondo, M. A1 is not a conservative extension of S4 but of S5. J Philos Logic 18, 321–323 (1989). https://doi.org/10.1007/BF00274070
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DOI: https://doi.org/10.1007/BF00274070