The Guarded Fragment (GF) of was introduced in 1996 by Hajnal Andréka, Johan van Benthem and István Németi, as a decidable fragment of first-order logic that aims to explain the attractive algorithmic and model theoretic behavior of modal logic. It subsequently gave rise to a larger family of decidable guarded fragments of first-order logic and second-order logic. These guarded fragments are, up to today, still actively studied and used in various application domains across different areas of computer science and artificial intelligence (e.g., data management, knowledge representation).

This workshop is a celebration of the 25th anniversary of GF. It will show case recent results, bringing together different strands of research, and offering an opportunity for reflection. The workshop is fully online, with a program consisting of 7 invited lectures, spread out across two days.

The Guarded Fragment (GF) of was introduced in 1996 by Hajnal Andréka, Johan van Benthem and István Németi, as a decidable fragment of first-order logic that aims to explain the attractive algorithmic and model theoretic behavior of modal logic. It subsequently gave rise to a larger family of decidable guarded fragments of first-order logic and second-order logic. These guarded fragments are, up to today, still actively studied and used in various application domains across different areas of computer science and artificial intelligence (e.g., data management, knowledge representation).

This workshop is a celebration of the 25th anniversary of GF. It will show case recent results, bringing together different strands of research, and offering an opportunity for reflection. The workshop is fully online, with a program consisting of 7 invited lectures, spread out across two days.

In relation to the first chapter of "Mathematical Intuition" by Richard Tiszen, we will discuss some notions of Husserl's phenomenology that pertain to the categorial intuition.

Derek So will introduce us to some basic concepts of Husserl's phenomenology. We focus on intentionality, synthetic and eidetic intuition. Then we will try to see how Tieszen posits it in his program.

The Dutch Categories And Types Seminar is an inter-university seminar on type theory, category theory, and the interaction between these two fields. It provides a forum for discussion, collaboration, and dissemination to researchers in type theory and category theory working in the Netherlands.

In person location: Utrecht, Kromme Nieuwegracht 80, room 1.06. This event will also be broadcast online, contact the organizer for more information.

Ludo Waltman is professor of Quantitative Science Studies and deputy director at the Centre for Science and Technology Studies (CWTS) at Leiden University. He does research in the fields of bibliometrics and scientometrics, with a special emphasis on applications in research management and science policy. In his talk 'Are we all biased? The complexity of the diversity puzzle', Ludo will describe how informetric research and methods allow for a better understanding of diversity in the research system. Please see full abstract here. The talk will be followed by a reception with snacks and drinks in the ILLC Common Room.

Is there a relation of logical consequence in natural language? Logicality, in the philosophical literature, has been conceived of as a restrictive phenomenon that is alien to the complex and messy character of natural language. In this talk, I will claim that there is a relation of logical consequence in natural language, and moreover, that it is the subject matter of the bulk of current theories of formal semantics. I employ the framework of semantic constraints (Sagi 2014), which generalises the Tarskian definition of logical consequence. I apply the widely accepted criterion of invariance under isomorphisms (Sher 1996) generalised to the framework of semantic constraints (Sagi 2022), as well as a theory of Glanzberg (2014) to delineate the relation of logical consequence in natural language.

This time we go to the hands-on phenomenological view of intuition. We read the second chapter of Mathematcial Intuition.

Logicians participating in this conference stand united for Peace. This event is used to collect financial aid for two specific causes: (a) We financially help our colleagues at universities in Ukraine, who are either displaced or have lost their homes, and thus are in urgent financial need. (b) We support the charitable fund 'Voices of children' which provides humanitarian aid and assists in Ukraine with the on-going evacuation processes.

As the world urgently needs more logic and rationality, Logic4Peace creates a platform for logicians from around the world to present their work in any area of logic.

All participants are asked to register for the conference. The registration fees will be entirely used to offer financial aid to Ukraine to help our colleagues and Voices of Children. We invite academic institutions and organizations to sponsor this online logic event.

Signed by the Co-Organizing Associations and Institutions.

Among the variety of possible solutions to the paradoxes of naive set theory, suggestions made by the mathematician Heinrich Behmann (1891--1970) appear to be particularly remarkable (even though they are commonly unknown today). From Behmann’s point of view, the paradoxes do not represent proper contradictions, but rather “meaningless” expressions that can be avoided by a simple and purely syntactical criterion. The main goal of my talk is to provide a partial confirmation of Behmann’s view. To this end, I will present a new system of natural deduction strongly inspired by Behmann’s analysis of the set-theoretical paradoxes. It will be demonstrated that a certain subclass of the proofs in our system has the normalization property: every deduction in this class may be transformed into a “cut-free” proof. As a corollary, it then follows that the propositional fragment of our system is in fact consistent. In the last part of the talk, I will discuss some open problems and closely related approaches such as the system of “Fitch-Prawitz Set Theory”.

Logicians participating in this conference stand united for Peace. This event is used to collect financial aid for two specific causes: (a) We financially help our colleagues at universities in Ukraine, who are either displaced or have lost their homes, and thus are in urgent financial need. (b) We support the charitable fund 'Voices of children' which provides humanitarian aid and assists in Ukraine with the on-going evacuation processes.

As the world urgently needs more logic and rationality, Logic4Peace creates a platform for logicians from around the world to present their work in any area of logic.

All participants are asked to register for the conference. The registration fees will be entirely used to offer financial aid to Ukraine to help our colleagues and Voices of Children. We invite academic institutions and organizations to sponsor this online logic event.

Signed by the Co-Organizing Associations and Institutions.

The Nordic Online Logic Seminar (NOL Seminar) is organised monthly over Zoom, with expository talks on topics of interest for the broader logic community. The seminar is open for professional or aspiring logicians and logic aficionados worldwide.

This is the announcement for the next talk. Those who wish to receive the Zoom ID and password for it, as well as further announcements, can subscribe here:https://listserv.gu.se/sympa/subscribe/nordiclogic .