The main purpose of this paper is to provide a critical analysis of Edmund L. Gettier's argumentation against adequacy of the classical theory of knowlegde. The critic consists in showing that in both Gettier counterexamples one of two situations takes place: either at least necessary condition specified by the classial definition of knowledge remains unsatisfied (so that the counterargument failed to be valid), or all conditions are satisfied while saying we have to do with knowledge is not counterintuitive. The major step of the argumnetation is to justify a prima facie unacceptable claim that one cannot simultaneously believe that p and that p or q. The analysis is preceded by an attempt to locate the philosophical concept of knowledge in proper contexts of the verb 'to know that' usage in ordinary language.
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