The paper seeks a perfectly general argument regarding the non-contingent limits to any (human or non-human) knowledge. After expressing disappointment with the history of philosophy on this score, an argument is grounded in Fitch’s proof, which demonstrates the unknowability of some truths. The necessity of this unknowability is then defended by arguing for the necessity of Fitch’s premise—viz., there this is in fact some ignorance.

The purpose of this paper is to mark a significant difference between classical and several non-classical prepositional calculi. The argument presupposes familiarity with Kripke/Hintikka semantics for modal logic. The non-classical systems are Hintikka's logic of belief and alethic modal systems which have Kripke/Hintikka semantics. The difference is marked by showing that the semantic validity operator in classical logic behaves as a normal alethic necessity-operator while the non-classical semantic validity operators behave as normal deontic ought-operators. The crucial step is showing that (...) a formula, valid by non-classical semantics, can be falsified. I show that the negation of a non-classical thesis can be added to a consistent set of formulae without making the set inconsistent or any other set inconsistent. This is shown by observing that consistent sets of formulae do not need to be related to other consistent sets by any of the alternativeness relations of Kripke/Hintikka model structures for non-classical systems. The deontic behavior of non-classical semantical validity operators is interpreted as showing that being a thesis of a non-classical system means, not that the thesis is a logical truth, but that the thesis is the content of a norm on how we ought to use, crucial terms such as ‘believe’ and ‘necessity’. (shrink)

The logic of ‘being informed’ gives a formal analysis of a cognitive state that does not coincide with either belief, or knowledge. To Floridi, who first proposed the formal analysis, the latter is supported by the fact that unlike knowledge or belief, being informed is a factive, but not a reflective state. This paper takes a closer look at the formal analysis itself, provides a pure and an applied semantics for the logic of being informed, and tries to find out (...) to what extent the formal analysis can contribute to an information-based epistemology. (shrink)