Colloquium Logicae Web Conference – CLE/Unicamp

Link permanente para participar dos seminários /

Permanent link to participate of the seminars:

Colloquium Logicae at CLE is now partner of the “Logic Supergroup”

The logic seminars connected to the course HF912 have been cancelled due to the interruption of activities at Unicamp in face of the Coronavirus from March 13th, with the final date to be evaluated.

Aa all scheduled in-person meetings have been  cancelled, we are inaugurating a virtual session of the  Colloquium Logicae, traditional conferences held the Centre for Logic, Epistemology and the History of Science at Unicamp, now linked to the “Logic Supergroup”. The website is:

Next scheduled  talks via “Conferência Web”:

Please enter as  “anonymous” unless you have an RNP account

September 8th, 2020 (4:00 PM, GMT -7 hours) – Alfredo Roque Freire

Intentional theory dichotomy and twisted models of set theory

Centre for Logic, Epistemology and the History of Science

University of Campinas-Unicamp, Brazil

Abstract. Two modes of description were familiar to modern mathematicians: (i) descriptions of mathematical types to be satisfied by various structures, such as rings, fields, monoids; and (ii) intentional descriptions, which seek to specify mathematical objects as in geometry, arithmetic and real analysis. Due to the various limiting theorems in relation to formal systems (e.g. G\”odel’s incompleteness and Loweinhein-Skolem theorems), it has become common to maintain that there is no sharp boundary between intentional and non-intentional theories. Since it is not possible to fix a single model for first order arithmetic, its axioms work in a similar way to axioms of general algebraic structures. This conclusion is the result of the following dichotomy: either there are precise and unambiguous ways to describe general collections of objects or there is no clear boundary between intentional theories and non-intentional theories. However, recent results on interpretability [1,2,3] develop restricted versions of absoluteness regarding theories historically considered to be intentional. In fact, models of arithmetic and set theory are unique with respect to bi-interpretations. We will argue that these results allow us not only to recover the dichotomy that separates intentional from non-intentional theories, but still remain compatible with pluralism regarding theories such as arithmetic and set theory.

Finally, we will show to what extent conditions of absoluteness may be used as sufficient to incorporate non-classical set theories to the multiverse. We believe this absoluteness conditions are possibly obtained for the novel twisted valued models developed by Carnielli and Coniglio [4]. We will argue that these paraconsistent models have the virtue of being sufficiently rigid, and thus may be successfully included in the multiverse.

[1] Friedman, H. M., & Visser, A. (2014). When bi-interpretability
implies synonymy. Logic Group Preprint Series, 320, 1-19.

[2] Enayat, A. (2017). Variations on a Visserian theme. arXiv preprint

[3] Freire, A. R., & Hamkins, J. D. (2020). Bi-interpretation in weak
set theories. arXiv preprint arXiv:2001.05262.

[4] Carnielli, W., & Coniglio, M. E. (2019). Twist-valued models for
three-valued paraconsistent set theory.
 Logic and  Logical Philosophy,  ON LINE FIRST:

August 12th, 2020 (2:00 PM, GMT -3 hours) – Alfredo Roque Freire

Unreducible features of set theories

Centre for Logic, Epistemology and the History of Science

University of Campinas – Unicamp

Abstract. The universalist position in set theory maintains that there is only a single, maximal universe of sets and, as a result, all sentences about these objects are ideally verifiable. Often, those who subscribe to this view are committed to offering a sensible account to alternative universes familiar to many mathematicians. In this article, we will analyze the reduction strategies offered by universalists. Recently, Enayat in [1] proved that no two models of ZF are bi-interpretable, while Hamkins and I in [2] proved that no two well-founded models of ZF are mutually interpretable. In view of these results, we will argue that the range of the construction for alternative universes in a single universe is limited. Thus, the adherents of an alternative universe have sufficient grounds to reject the alleged copy offered by the universalist as a faithful copy. Finally, we will argue that the reasons for adding new elements to the multiverse should be specific instead of being the result of an emulation in a previously known universe.

[1] Enayat, A. (2017). Variations on a Visserian theme. arXiv preprint

[2] Freire, A. R., & Hamkins, J. D. (2020). Bi-interpretation in weak
set theories. arXiv preprint arXiv:2001.05262.

June 17th, 2020 (2:00 PM, GMT -3 hours) – Itala M. L. Loffredo D’ Ottaviano

Remarks on a nice theorem of Monsieur Glivenko

Department of Philosophy

Centre for Logic, Epistemology and the History of Science

University of Campinas – Unicamp

Abstract. In this talk I will discuss some less known historical and conceptual points behind the famous double-translation theorem of Valery
Ivanovich Glivenko.

July 1st, 2020 (2:00 PM, GMT -3 hours) – Ekaterina Kubyshkina

Ignorance: a truth-functional perspective

Center for Logic, Epistemology and History of Sciences

University of Campinas – Unicamp

Abstract. I will present a family of four-valued logics, dubbed logics of rational agent, where the epistemic state of an agent is represented truth-functionally. In particular, these logics permit one to formalize the fact of being ignorant of or knowing some truth at the level of valuations, without the explicit use of epistemic operators. On the basis of this semantics several sound and complete systems will be provided. Moreover, these systems, extended by alethic modalities of necessity and possibility, will be applied to the analysis of an epistemological problem known as knowability paradox, or Church-Fitch paradox.

July 15th, 2020 (2:00 PM, GMT -3 hours) – Marcelo Coniglio

Logics of Formal Inconsistency and a solution to the problem of replacement

Department of Philosophy

Centre for Logic, Epistemology and the History of Science

University of Campinas – Unicamp

Abstract. One of the most desired properties of a logical system is that it can be algebraizable, in the sense that an algebraic counterpart of the deductive machinery could be found. Since the inception of da Costa’s paraconsistent calculi, an algebraic equivalent for such systems have been searched. It is known that these systems are not algebraizable neither in the standard sense nor in the sense of Blok-Pigozzi. The same negative result holds for several systems of the hierarchy of paraconsistent logics known as Logics of Formal Inconsistency (LFIs). In this talk I shall expound a solution for this problem, showing how LFIs can satisfy the replacement property. The weakest LFI satisfying replacement presented is called RmbC, and I intend clarify the role of the BALFI (Boolean algebras with LFI operators) and neighborhood semantics for RmbC. This is a joint work with Walter Carnielli and David Fuenmayor.

20/05/2020 (2:00 PM, GMT – 3 hours) – Abílio Rodrigues

On some recent criticisms to the logics of evidence and truth

Department of Philosophy

UFMG, Belo Horizonte

Abstract. The aim of this talk is to clarify some misunderstandings and to reply to some criticisms that have been made on logics of evidence and truth (LETs) and the epistemic approach to paraconsistency. Some new developments of LETs will also be presented and discussed.

30/04/2020 (11:00 a.m.) – Juliana Bueno-Soler

Plain fibring combination of polynomic logics

Juliana Bueno-Soler

School of Technology

University of Campinas-Unicamp

Limeira, SP, Brazil

Via Zom, co-organized in cooperation with the Munich Center for
Mathematical Philosophy (MCMP) – LMU, Munich, Germany

Abstract. The combination of logics is a powerful technique which permits systematic generation of new logic systems. Combinations can be homogeneous or heterogeneous depending whether the systems combined are or not presented by the same proof methods. In this talk I consider the homogeneous technique of Plain Fibring which is dedicated to combining logics defined by matrix semantics. The polynomial ring calculus is a technique which permits to describe a logical system by a set of finite polynomials defined over an appropriate field. This method can be applied to different classes of logics such as many-valued logics, modal logics, paraconsistent logics and first order logic. A natural question is whether it is possible to obtain systematically a polynomial ring calculus for the combined systems. In order to answer this question we define the method of plain fibring of polynomic logics (polynomial representations of matrix logics), as a companion to the method of combining matrix logics, proposed by M. E. Coniglio and V. Fernandez and fully developed in [1] and [2].


[1] W.A. Carnielli, M.E. Coniglio, D. Gabbay, P. Gouveia, and C. Sernadas. Analysis and Synthesis of Logics. Springer, 2007.

[2] M.E. Coniglio and V. Fernandez. Plain Fibring and direct union of logics with matrix semantics. In B. Prasad, editor, Proceedings of the 2nd Indian International Conference on Artificial Intelligence, volume 1, pages 1590-1608. IICAI, 2005.

O seminário do dia 25/03/2020 está cancelado

Em função da paralisação das atividades de 13/03 até 29/03 na Unicamp, o seminário do professor Olivier Rioul está cancelado. O demais seminários previstos no cronograma estão mantidos em suas respectivas datas.