Paul Weingartner

SummaryIn the first part of the paper necessary conditions for the rationality of the notions of belief, knowledge, and assumption are given: Among the different conditions it is stressed that one needs two different concepts of belief, one such that if someone knows something he also believes it, the other exclusive such that if someone knows something he need not to believe it and if he believes it he does not yet know it. Another important point is that deductive infallibility has to be rejected as not being a property of human rationality. Similarly it is not a property of human rationality to know all logical true statements.The second chapter offers a deductive system which meets these and additional conditions of human rationality. The third chapter contains the semantics of the deductive system.RésuméDans le premier chapitre ľauteur énumére des conditions nécessaires à la rationalité des concepts croire, savoir et admettre. Entre autres, il relève qu'il faut distinguer au moins deux concepts croire, qui satisfont ľun àľénoncé: quand quelqu'un sait quelque chose, il la croit aussi, ľautre plus exclusif à: quand quelqu'un sait quelque chose, il n'a pas besoin de la croire et quand quelqu'un la croit , il ne la sait pas . Un autre point très important est que ľinfaillibilité déductive doit être rejetée comme n'appartenant pas à la rationalité humaine. Idem pour la connaissance de tous les énoncés logiquement vrais.Le deuxième chapitre décrit un système déductif qui remplit ces conditions de rationalité . Le troisième, la sémantique de ce système.ZusammenfassungIm ersten Kapitel werden notwendige Bedingungen für die Rationalität der Begriffe Glauben, Wissen und Annehmen gegeben: Unter anderem wird hervorgehoben, dass minde‐stens zwei verschiedene Begriffe von Glauben nötig sind; einmal so, dass gilt: wenn einer etwas weiss, dann glaubt er es auch, und dann auch im exklusiven Sinn: wenn einer etwas weiss, dann braucht er es nicht zu glauben und wenn einer etwas glaubt, dann weiss er es nicht. Ein anderer sehr wichtiger Punkt ist, dass deduktive Infallibilität (d.h. dass man von dem

This article proposes a basic logic for application in physics dispensing with the Principle of Excluded Middle. It is based on the article “Matrix Based Logics for Application in Physics (RMQ) which appeared 2009. In his article with Stachow on the Principle of Excluded Middle in Quantum Logic (QL), Peter Mittelstaedt showed that for some suitable QLs, including their own, the Principle of Excluded Middle can be added without any harm for QL; where ‘without any harm for QL’ means that the basic desiderata and the basic results (theorems) of those QLs remain satised in the sense that they avoid the well known difficulties with commensurability and distributivity.In the following article I want to show that the basic desiderata and results (theorems) of RMQ (of avoiding the well-known difficulties with commensurability, distributivity, fusion and Bell’s inequalities) remain satised if by introducing a strong negation (or strong negation and disjunction) the resulting weak intuitionist system RMQI dispenses with the Principle of Excluded Middle; it becomes either invalid or not strictly valid

The first part of the papaer contains desiderata for a realistic epistemic system as opposed to idealistic ones. One of the main characteristics of idealistic epistemic systems is their deductive infallibility or deductive omniscience. The system presented avoids deductive infallibility though having a strong concept of knowledge. The second part contains the theorems of the system. The system is detailed in so far as it distinguishes between two concepts of belief and one of assumption and interrelates them to the concept of knowledge. Though all concepts satisfy certain consistency criteria the strongest ones hold for the concept of knowledge; whereas a belief in or a assumption (assertion) of a proposition which has inconsistent consequences (not known or believed or assumed by the believer or assumer) does not entail the commitment of believing in (or assuming of) an explicit contradiction. Moreover the system contains a lot of distinctions and details concerning propositions with a second person involved like "a knows that b knows whether p is the case" etc. The third part of the paper contains the semantics of the system which consists of many-valued truth-tables. Since the matrices are finite the system is consistent and decidable.

Jaakko Hintikka's concept of belief (aBp) as presented in his Knowledge and Belief is such that in his epistemic logic aKp —> aBp is a thesis. This concept (B-belief) is one important kind of belief and can be contrasted with a different concept of belief (G-belief, denoted by 'aOp') not discussed in Hintikka's book. It is to some extent opposite to the one above in the sense that it is knowledge-exclusive, whereas Hintikka's is knowledge-inclusive. This is shown by the thesis aKp —> —laGp or aGp —> —laKp. My thesis is that this kind of belief is used as the belief in scientific hypothesis and as religious belief. Both G-belief and B-belief are applied to examples from physics and religion and consistency criteria are discussed for either concept.