Starting the Dismantling of Classical Mathematics

The Australasian Journal of Logic, 2021

We assess Meyer’s formalization of arithmetic in his [21], based on the strong relevant logic R and compare this with arithmetic based on a suitable logic of meaning containment, which was developed in Brady [7]. We argue in favour of the latter as it better captures the key logical concepts of meaning and truth in arithmetic. We also contrast the two approaches to classical recapture, again favouring our approach in [7]. We then consider our previous development of Peano arithmetic including primitive recursive functions, finally extending this work to that of general recursion.

Vestnik Tomskogo gosudarstvennogo universiteta. Filosofiya. Sotsiologiya. Politologiya, 2017

Synthese, 2006

The picture of mathematics as being about constructing objects of various sorts and proving the constructed objects equal or unequal is an attractive one, going back at least to Euclid. On this picture, what counts as a mathematical object is specified once and for all by effective rules of construction. In the last century, this picture arose in a richer form with Brouwer's intuitionism. In his hands (for example, in his proof of the Bar Theorem), proofs themselves became constructed mathematical objects, the objects of mathematical study, and with Heyting's development of intuitionistic logic, this conception of proof became quite explicit. Today it finds its most elegant expression in the Curry-Howard theory of types, in which a proposition may be regarded, at least in principle, as simply a type of object, namely the type of its proofs. When we speak of 'proof-theoretic semantics' for mathematics, it is of course this point of view that we have in mind. On this view, objects are given or constructed as objects of a ginen type. That an object is of this or that type is thus not a matter for discovery or proof. One consequence of this view is that equality of types must be a decidable relation. For, if an object is constructed as an object of type A and A and B are equal, then the object is of type B, too, and this must be determinable. One pleasant feature of the type theoretic point of view is that the laws of logic are no longer 'empty': The laws governing the type ∀x : A.F (x) = Π x:A F (x) simply express our general notion of a function, and the laws governing ∃x : A.

Elimination of quantifiers is shown to fail dramatically for a group of well-known mathematical theories (classically enjoying the property) against a wide range of relevant logical backgrounds. Furthermore, it is suggested that only by moving to more extensional underlying logics can we get the property back.

Mathematical Logic Quarterly, 2018

Elimination of quantifiers is shown to fail dramatically for a group of well-known mathematical theories (classically enjoying the property) against a wide range of relevant logical backgrounds. Furthermore, it is suggested that only by moving to more extensional underlying logics can we get the property back.

Manuscrito Revista Internacional De Filosofia, 1996

Husserl developed-independently of Frege-a semantics of sense and reference. There are, however, some important differences, specially with respect to the references of statements. According to Husserl, an assertive sentence refers to a state of affairs, which was its basis what he called a situation of affairs. Situations of affairs could also be considered as an alternative referent for statements on their own right, although for Husserl they were simply a sort of referential basis. Both Husserlian states of affairs and situations of affairs are extensional. Tarskian semantics can be rendered as a sort of state of affairs semantics. However, to assess adequately the existence of dual theorems in mathematics and, more generally, seemingly unrelated interderivable statements like the Axiom of Choice and its many equivalents, states of affairs (and truth-values) are not enough. We need a sort of refinement of the notion of a situation of affairs, namely what we have called elsewhere an abstract situation of affairs. We are going to introduce abstract situations of affairs as equivalence classes of states of affairs denoted by closed sentences of a given language which are true in the same models. We first sketch the procedure for a first-order many-sorted language and then for a second-order manysorted language.

Journal of Philosophical Logic

In order to prove the validity of logical rules, one has to assume these rules in the metalogic. However, rule-circular ‘justifications’ are demonstrably without epistemic value (sec. 1). Is a non-circular justification of a logical system possible? This question attains particular importance in view of lasting controversies about classical versus non-classical logics. In this paper the question is answered positively, based on meaning-preserving translations between logical systems. It is demonstrated that major systems of non-classical logic, including multi-valued, paraconsistent, intuitionistic and quantum logics, can be translated into classical logic by introducing additional intensional operators into the language (sec. 2–5). Based on this result it is argued that classical logic is representationally optimal. In sec. 6 it is investigated whether non-classical logics can be likewise representationally optimal. The answer is predominantly negative but partially positive. Never...

This paper brings up some important points about logic, e.g., mathematical logic, and also an inconsistence in logic as per Gödel's incompleteness theorems which state that there are mathematical truths that are not decidable or provable. These incompleteness theorems have shaken the solid foundation of mathematics where innumerable proofs and theorems have a place of pride. The great mathematician David Hilbert had been much disturbed by them. There are much long unsolved famous conjectures in mathematics, e.g., the twin primes conjecture, the Goldbach conjecture, the Riemann hypothesis, etc. Perhaps, by Gödel's incompleteness theorems the proofs for these famous conjectures will not be possible and the numerous mathematicians attempting to find the solutions for these conjectures are simply banging their heads against the metaphorical wall. Besides mathematics, Gödel's incompleteness theorems will have ramifications in other areas involving logic. This paper looks at the ramifications of the incompleteness theorems, which pose the serious problem of inconsistency, and offers a solution to this dilemma. The paper also looks into the apparent inconsistence of the axiomatic method in mathematics. [Published in international mathematics journal. Acknowledgments: The author expresses his gratitude to the referees and the Editor-in-Chief for their valuable comments in strengthening the contents of this paper.]

Activity and Sign, 2005

It is not sufficient to supply an instance of Tarski's schema,  "p" is true if and only if p  for a certain statement in order to get a definition of truth for this statement and thus fix a truth-condition for it. A definition of the truth of a statement x of a language L is a bi-conditional whose two members are two statements of a meta-language L'. Tarski's schema simply suggests that a definition of truth for a certain segment x of a language L consists in a statement of the form: