Algebrai logika; relativitáselmélet logikai struktúrájának vizsgálata = Algebraic logic; investigating the logical structure of relativity theory

Gödel, Einstein és Tarski hagyományait kívánjuk folytatni, elmélyítve a Gödel-Einstein együttműködés eredményeit is, és folytatva Tarski tudományegyesítési programmját. Ismert, hogy a logika és a matematika modern megalapozása Gödel és Tarski úttörő munkásságára vezethető vissza. Kevésbbé ismert, hogy Gödel 1948-tól majdnem élete végéig Einsteinnel szorosan együttműködve relativitáselméleten dolgozott, ahol ugyanolyan meghökkentő új horizontokat tárt fel mint logikában, és hogy Gödel relativitáselméleti gondolatai folytatásaként fogható fel a forgó fekete lyukak mai elmélete. Ezen előzmények folytatása a jelen projektum, mely Tarskival és munkatársaival való személyes együttműködés (pl. közös könyv) keretében kezdődött. Az alapgondolat a logika, algebra, geometria, téridőelmélet és relativitáselmélet egységben való művelése. Eredményeinkből egy példa: Nagy, lassan forgó fekete lyukakról bizonyítottuk, hogy a belsejében létrejövő un. zárt időszerű görbe (időhurok) létrejöttére vonatkozó szokásos irodalmi magyarázatok tévesek. Nem az un. drag effect (mozgó anyag magával vonszolja a téridőt) okozza a zárt görbéket, hanem egy egészen más jellegű hatás: a fénykúpok kinyílása a forgással ellentétes irányban. Az eredmény a General Relativity and Gravitation című folyóiratban jelenik meg. | The reported project intends to continue traditions of Gödel, Einstein and Tarski continuing the spirit of the Gödel-Einstein collaboration and pursuing Tarski's programme for unifying science. Modern logic and meta-mathematics was created (basically) by Gödel and Tarski. It is less well known that beginning with 1948 Gödel spent much time with Einstein and worked on relativity theory. Of course, he remained a logician in spirit. Gödel obtained fundamental breakthroughs in relativity like his ones in logic and foundations. The theory of general relativistic spacetimes not admitting a global Time was initiated by Gödel, and came to full blossom during the renaissance of black hole physics during the last 25 years. The present project was originally started in personal cooperation with Tarski and his collaborators. The idea is to study logic, algebra, geometry, spacetime theory and relativity in a strong unity. A sample result of ours: We proved about big, slowly rotating black holes that the usual explanation in the literature of why such black holes contain a closed timelike curve (CTC) is flawed. Namely, it is not the gravitational frame dragging effect which creates CTCs, instead, there is a completely different kind of effect in action there: light cones open up in the direction opposite to that of the rotation of the source and this goes on to such an extreme extent that CTCs are created. Our paper on this appears in the journal General Relativity and Gravitation

The Prolog Inference Model refutes Tarski Undefinability

The generalized conclusion of the Tarski and Gödel proofs: All formal systems of greater expressive power than arithmetic necessarily have undecidable sentences. Is not the immutable truth that Tarski made it out to be it is only based on his starting assumptions. When we reexamine these starting assumptions from the perspective of the philosophy of logic we find that there are alternative ways that formal systems can be defined that make undecidability inexpressible in all of these formal systems

Truth and Existence

Halbach has argued that Tarski biconditionals are not ontologically conservative over classical logic, but his argument is undermined by the fact that he cannot include a theory of arithmetic, which functions as a theory of syntax. This article is an improvement on Halbach's argument. By adding the Tarski biconditionals to inclusive negative free logic and the universal closure of minimal arithmetic, which is by itself an ontologically neutral combination, one can prove that at least one thing exists. The result can then be strengthened to the conclusion that infinitely many things exist. Those things are not just all Gödel codes of sentences but rather all natural numbers. Against this background inclusive negative free logic collapses into noninclusive free logic, which collapses into classical logic. The consequences for ontological deflationism with respect to truth are discussed

Intuitionism and the Modal Logic of Vagueness

Intuitionistic logic provides an elegant solution to the Sorites Paradox. Its acceptance has been hampered by two factors. First, the lack of an accepted semantics for languages containing vague terms has led even philosophers sympathetic to intuitionism to complain that no explanation has been given of why intuitionistic logic is the correct logic for such languages. Second, switching from classical to intuitionistic logic, while it may help with the Sorites, does not appear to offer any advantages when dealing with the so-called paradoxes of higher-order vagueness. We offer a proposal that makes strides on both issues. We argue that the intuitionist’s characteristic rejection of any third alethic value alongside true and false is best elaborated by taking the normal modal system S4M to be the sentential logic of the operator ‘it is clearly the case that’. S4M opens the way to an account of higher-order vagueness which avoids the paradoxes that have been thought to infect the notion. S4M is one of the modal counterparts of the intuitionistic sentential calculus and we use this fact to explain why IPC is the correct sentential logic to use when reasoning with vague statements. We also show that our key results go through in an intuitionistic version of S4M. Finally, we deploy our analysis to reply to Timothy Williamson’s objections to intuitionistic treatments of vagueness

Do Goedel's incompleteness theorems set absolute limits on the ability of the brain to express and communicate mental concepts verifiably?

Classical interpretations of Goedel's formal reasoning imply that the truth of some arithmetical propositions of any formal mathematical language, under any interpretation, is essentially unverifiable. However, a language of general, scientific, discourse cannot allow its mathematical propositions to be interpreted ambiguously. Such a language must, therefore, define mathematical truth verifiably. We consider a constructive interpretation of classical, Tarskian, truth, and of Goedel's reasoning, under which any formal system of Peano Arithmetic is verifiably complete. We show how some paradoxical concepts of Quantum mechanics can be expressed, and interpreted, naturally under a constructive definition of mathematical truth.Comment: 73 pages; this is an updated version of the NQ essay; an HTML version is available at http://alixcomsi.com/Do_Goedel_incompleteness_theorems.ht

Definability and Undefinability of Truth

This thesis will focus on Tarski’s work, so the Section 2 starts with him, giving an overview of the elements of his theory of truth, leading to a presentation of his theorem in 2.3. In the rest of the paper, proposals for solving the problem of internalization of the concept of truth and the paradoxes arising from this problem with some of the proposed solution are considered. Section 3. will quickly introduce the Liar paradox and once more explicitly state Tarski’s solution, followed by the so called “revenge of the liar”; a liar type sentence which cannot be avoided even by using Tarski’s solution to the original liar. After that, Section 4. will introduce Kripke’s Theory of Truth and his take on truth and solving t he Liar paradox using paracomplete logic, while Section 5. will examine some further attempts in answering the aforementioned problems in the context of paraconsistent logic

Definability and Undefinability of Truth

This thesis will focus on Tarski’s work, so the Section 2 starts with him, giving an overview of the elements of his theory of truth, leading to a presentation of his theorem in 2.3. In the rest of the paper, proposals for solving the problem of internalization of the concept of truth and the paradoxes arising from this problem with some of the proposed solution are considered. Section 3. will quickly introduce the Liar paradox and once more explicitly state Tarski’s solution, followed by the so called “revenge of the liar”; a liar type sentence which cannot be avoided even by using Tarski’s solution to the original liar. After that, Section 4. will introduce Kripke’s Theory of Truth and his take on truth and solving t he Liar paradox using paracomplete logic, while Section 5. will examine some further attempts in answering the aforementioned problems in the context of paraconsistent logic