ON S4 AS THE LOGIC OF JUSTIFIED KNOWLEDGE

LEGRIS, JAVIER

THE JOURNAL OF NON CLASSICAL LOGIC

CLE/UNICAMP

Lugar: CAMPINAS; Año: 1991 vol. 8 p. 103 - 117

0102-3411

Some years ago W. lenzen and F. v. Kutschera argued that S4.2 and S.4.4 (but not S4) are the "logics of knowledge". In this paper I give good reasons to consider S4 as the "logic of justified knowledge". From the basis of a doxastic system for the notion of justified belief and the defintion of knowledge as "true justified belief" I construct an epistemic counterpart to S4, and I show semantically that at most this system is derivable from these assumptions. In this sense, the original conjecture of J. Hintikka about S4 as the excat tantamount to the logic of "real" knowledge becomes defensible.