The number of logic and philosophy seminars has grown exponentially during these Coronavirus times of ours. I am listing here some of the meetings that compete for our time and disposition with the 'Working Logician'.
There is the Logicians in Quarantine, organized by the
Brazilian Logic Society / Logic Interest Group/Brazilian Computing Society
website at http://sbl.org.br/pmwiki.php/LQ/Quarentena.
The Proof Society Seminar https://www.proofsociety.org/proof-theory-seminar/slides.html
The SuperGroup Logic Seminar https://sites.google.com/view/logicsupergroup/the-logic-supergroup
The Buenos Aires logic group calls its seminar Seminario de Lógica Iberoamericana (SeLoI), https://ba-logic.com/seloi/
There are many other seminar series, but the point of this post is to list the talks in thee PUC-Rio seminar, organized by Luiz Carlos Pereira as real working seminars for his students. In reverse cronological order the meetings last semester were:
16/12/2020 Title: Trying to understand resource consciousness
Prof. Elaine Pimentel DMAT/UFRN
Abstract:
We look at substructural calculi from a game semantic point of view,
guided by certain intuitions about resource conscious and, more
specifically, cost conscious reasoning. To this aim, we start with a
game, where player I defends a claim corresponding to a
(single-conclusion) sequent, while player II tries to refute that claim.
Branching rules for additive connectives are modeled by choices of II,
while branching for multiplicative connectives leads to splitting the
game into parallel subgames, all of which have to be won by player I to
succeed. The game comes into full swing by adding cost labels to
assumptions, and a corresponding budget. Different proofs of the same
end-sequent are interpreted as more or less expensive strategies for I
to defend the corresponding claim. This leads to a new kind of labelled
calculus, which can be seen as a fragment of SELL (subexponential linear
logic). Finally, we generalize the concept of costs in proofs by using a
semiring structure, illustrate our interpretation by examples and
investigate some proof-theoretical properties.
The talk assumes *no prior knowledge* on games or substructural logic. Only a basic notion of sequent systems is advisable.
This is a joint work with Timo Lang, Carlos Olarte and Christian G. Fermüller.
December 09, 2020 TITLE. A Constructivist Reading of the Epsilon Calculus
SPEAKERS. Mattia Petrolo (UFABC), Elio La Rosa (LMU Munich)
ABSTRACT. The aim of this work is to provide a constructivist reading of Hilbert's epsilon calculus.
This goal is achieved in two steps, one philosophical and the other logical. First, we investigate
in which sense the epsilon calculus can be seen, from a broadly Kreiselian perspective, as a way
of providing a constructive analysis of classical logic and mathematics. In order to highlight the
constructive aspects of this calculus, our strategy is to implement it
in the general proof theoretic setting provided by (a variant of) Gentzen's sequent calculus.
In particular, a cut-elimination algorithm for a version of the epsilon calculus is provided.
Thus, in the second part of this work, we show how a given notion of constructivity can be
displayed via the epsilon calculus.
Extra, as it happened in Prof Giorgio Venturi's seminar series 1/12/2020 Title:
A universal graph-theoretic criterion for relevance
Prof Peter Verdée
Abstract
In this talk I present work in progress
by my FNRS MIS funded research team (Pilar Terres, Pierre
Saint-Germier, Joao Daniel Dantas) working on
explanatory inference. We came up with a criterion for relevance of the
entailment relation, relative to a given logic. One of the weak criteria
of relevance presented in the literature is the principle of variable
sharing: if a (multiple conclusion) sequent is relevantly valid then
every formula in the sequent needs to have at least one variable in
common with the other formulas in the sequent. I present a couple of
cases from which it should be clear that this criterion (while being
necessary) certainly is not sufficient for relevance. We solve these
problems by analyzing relevance in terms of connectivity. The idea is to
say that a sequent is relevantly valid iff
a connected graph (of a specific nature) can be established that
contains all of the formulas of the sequent. The basis of this idea is
the concept of a constitution of a logic. This
is a set of sequents that express full logical grounds of all formulas
of the language of the logic (the grounded formula of each sequent is
underlined, the non-underlined formulas are the partial
grounds--examples are "A,B>A&B", "A&B>A" and "A, A->B >
B" in the case of classical logic). The partial grounds (the
non-underlined formulas) of each formula determine the way in which
formulas of the potentially relevant sequents can be connected to other
formulas of the sequent. We will present and motivate the criterion,
give a couple of examples, and present some graph-theoretical results
concerning this criterion.
02/12/2020 The pragmatic structure of mathematics
Prof. Giorgio Venturi
We explore many linguistic facets that permeate mathematical
proofs. To do so, we analyze mathematics through the lens of speech act
theory, focusing on those illocutionary aspects which are peculiar to
the mathematical discourse. Our analysis includes both the single speech
acts that occur in proofs and the delicate interplay of such acts.
26 y 27 november 2020 Title: A maximalist view on the meaning of logical connectives
Profa. Pilar Terrés
Abstract: The aim of this talk is to explore the consequences that
minimalism for logical connectives (the view that the meaning is
determined by their left and right rules in different sequent calculus
languages), together with logical pluralism, has in our undertanding of
logical connectives in natural language. I want to suggest an
alternative view: the meaning of logical connectives is determined by
their left and right rules in the full-structural classical logic, and
hence, the meaning of the logical vocabulary is not necessarily
determined by their inferential role in the different logics that a
pluralist endorses.
25/11/2020 Title: The BA plan: how to recapture classicality in the ST-hierarchy
Prof. Eduardo Barrio
Abstract. Anti-exceptionalism
about logic is the approach that logical theories have no special
epistemological status. Such theories are continuous with scientific
theories. Contemporary anti-exceptionalists include data about semantic
paradoxes as a part of the logical evidence. Exploring the Buenos Aires
plan, the recent development of the metainferential hierarchy of ST-logics shows that there are multiple options to deal with such paradoxes. There is a whole ST-based hierarchy, of which LP and ST itself are only the first steps. The logics in this hierarchy and STω are
also options to deal with semantic paradoxes. This talk explores these
responses analyzing some reasons to go beyond the first steps. I
show that LP, ST and the logics of the ST-hierarchy
offer different diagnoses for the same evidence: the inferences and
metainferences the agents endorse in the presence of the
truth-predicate. But even if the data is not enough to adopt one of
these logics, there are other elements to evaluate the revision of
classical logic. How close should we be to classical logic? Which logic
should be used during the revision? Should a logic be closed under its
own rules? How could a logic obey the validities they contain? And
mainly, Which is the best explanation of the logical principles to deal
with semantic paradoxes? I will argue that, if the answers to these
questions are provided by an antiexceptionalist perspective, ST-metainferential logics in general—and STTω in particular—are the best available options.
18/11/20: Reflective Equilibrium and Logical Pluralism
Prof Abílio Rodrigues
The aim of this talk is to propose a pluralist view of logic that
makes possible a peaceful coexistence between classical logic and some
paraconsistent and paracomplete logics. The central point is to
understand the inference rules of classical, intuitionistic, Nelson's
N3, Belnap-Dunn 4-valued logic, and BLE (the basic logic of evidence)
as a result of two ingredients: i. inferential practices based, in
each case, on a fundamental semantic notion; ii. reflective
equilibrium. The result of combining logical pluralism with reflective
equilibrium is a weak form of revisionism, according to which logic is
not really revised. The idea is rather that different formal systems
are concerned with different properties of propositions, and therefore
are appropriate to different contexts of reasoning. (Joint work with
Marcos Silva)
16/11/20: Hermann IV
11/11/20: Hermann III
4/11/20: Hermann II
28/10/20: Título: Redundancy in huge Natural Deduction proofs or how to obtain polynomial certificates for Non-Hamiltonian graphs.
by Edward Hermann Haeusler and Lew Gordeev
In this talk, we take the family of normal
proofs of the tautologies of the purely implicational minimal logic as a
family of super-polynomially bounded or huge sized objects. We use the
notion of (atomic) expanded and mapped normal (EmND) proofs to prove
that almost every huge EmND proof that has a linearly bounded height
is highly redundant. We show that for almost all proofs of such family
there is at least one sub-proof or derivation that is repeated
super-polynomially many times.
This result points out to a refinement of
compression methods previously presented and an alternative and simpler
proof that CoNP=NP.
30 set 2020 10:30 AM São Paulo: Veloso-type Solutions to Metapuzzles
Prof. Frank Thomas Sautter
Abstract. I introduce a method for solving metapuzzles inspired by
Paulo Veloso's General Theory of Problems. This method is not the
most efficient one, but its virtues include faithful modeling of the
flow of information and logical standardization through the use of the
same first-order predicates in all its applications.
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| 14 Oct 2020: Title: It's unlikely that there are good arguments for logical monism |
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professor Diogo H.B. Dias (DF/UENP & DF/USP):
Abstract: The aim of this talk is to investigate some arguments for
logical monism, and to show how, with minor modifications, these
arguments could be used to defend the adequacy of different logics.
Hence, as a defense of logical monism, they all fail. From this
analysis, we'll present a different kind of pluralism, based on the
notion that logic is relative to its domain of application. |
(photo by 
