World Logic Day 2021

14. January 2021

In the city of Kurt Gödel, Ludwig Wittgenstein, and the Vienna Circle, mathematical logic and its application to the sciences have a long and rich tradition.

The Vienna Center for Logic and Algorithms at Vienna University of Technology (VCLA at TU Wien) represents six research groups building on the aforementioned work in a wide range of disciplines, including computer science, mathematics, artificial intelligence, philosophy, linguistics, and many more.

Ambassadors of logic

The following renowned scientists have provided us with short statements on the rationale for the celebration of the World Logic Day 2021.

There's nothing you can do that can't be done Nothing you can sing that can't be sung Nothing you can say, but you can learn how to play the game - It's easy
All you need is logic
All you need is logic
All you need is logic, logic
Logic is all you need!
Arnon Avron
Tel Aviv University
Logic rules the structure of the world, and if we only let it, also our actions in the world. Logic is our strongest ally in being coherent in reasoning, fair in criticizing, and clear-headed about the scope and limits of thinking.
In Logic, like in all creative activities, one should never dismiss any idea, however bizarre it may seem at first sight, and should always be encouraged to turn it into something interesting and new. This is what happens with the most talented musicians: no sequence of notes is ‘wrong’ in itself, you just need to put it in the appropriate context and it will sound right.
Marcello D’Agostino
University of Milan
Mathematical logic, which has played an important role in many areas of computer science, is now increasingly recognized as a crucial part of the infrastructure of what is now the “hot topic” in computer science, namely artificial intelligence.
Ron Fagin
IBM Almaden Research Center
Logic doesn’t tell us what is true, but whether our reasoning about truth is coherent. We have many ways of reasoning: on what people know, on changes over time, on consequences of actions, etc. Rules of the games differ, but we can’t play a game unless we know what the rules are.
Melvin Fitting
Lehman College
Based on the assumption that the Almighty has created a coherent being, and that He has sprinkled a little logic in our minds, a Human Being going about his daily activities is the ultimate logical system, in the same way that the created physical universe, running its course, is the ultimate complex mathematical system. The final steps in the evolution of logic into the far future is to be able to completely model the logic in our heads! Thus I say- I am Logic
Dov Gabbay
King's College London
Logic is the science of deductive reasoning. This includes reasoning about foundations of some disciplines (like mathematics and computer science); it includes also effective and computer-assisted reasoning for acquiring information to be spent in real life.
Silvio Ghilardi
University of Milan
That humans can reason is amazing; that reasoning can be captured by logical principles is intriguing; that logic can be used in many other ways is surprising. Thus logic amazes, intrigues, and surprises, among other things.
The computational complexity of a problem — how hard it is to solve — is captured by the richness of the logical language needed to specify the problem. For this reason among others, logic has a critical role to play in building dependable software.
Over the years, logic has provided the concepts, methods, and technical tools for confronting the crisis in the foundations of mathematics, for resolving linguistic paradoxes, and for developing computer science as an intellectual discipline.
Phokion Kolaitis
UC Santa Cruz
Applications of formal logic in Artificial Intelligence have resulted in improvements of logic, which can also be used by humans to improve their own natural intelligence. IIn particular, they can be used to improve the clarity and coherence of natural language communications, with special significance in the field of law.
Robert Kowalski
Imperial College London
Logic has made an impact in Mathematics by helping to organize its foundation and structure its proofs. However, logic and the theory of proofs have made a much broader impact within Computer Science, where it provides new designs and new languages as well as foundational results and far-reaching connections.
Logic is the fertile ground where axioms blossom into theorems, centuries-old theorems are distilled into definitions, and ground-breaking definitions instill new life into axioms originally devised for reasons of technical convenience.
When all is said and done, what's left, what stays, from being human, is Logic. Logic removes all the flesh and ornaments, and gives us the underlying bones of what we know. Whether it intends to do so or not, logic turns out to be a moral compass. We overlook it at our own peril, as Logic is even more inexorable than taxes and death.
During the many years I have been doing research in computer science I have explored many different topics, including logic programming, concurrency theory, security and privacy. In this scientific journey, logic has been my constant companion and my reference point. It has helped me to structure my thoughts and my way of approaching problems, and has provided useful notions for theories and methods that I have proposed.
"All generalisations - perhaps except this one - are false." Kurt Gödel
In Through the Looking Glass, Lewis Carroll has Tweedldee say: ‘Contrariwise, if it was so, it might be; and if it were so, it would be: but as it isn't, it ain't. That's logic.’ This is, of course, a parody. To reason correctly is precisely to avoid such tangles. That’s logic.
Proofs and computations are the most fundamental concepts pertaining to virtually any intellectual human activity. Mathematical logic has been remarkably successful in understanding these concepts, as well as intricate relations between them, in a rigorous, mathematical way. This, in my view, is one of its crowning achievements.
Logic and formal reasoning play a key role in ensuring correctness and safety of many software and hardware systems, as well as in understanding the behavior of contemporary AI systems. I am really excited to be an ambassador of the World Logic Day 2021.
The world needs more logic! Logic is the core engine which guides our understanding of the complex epistemic social environment in which we live and operate. Gaining more knowledge and understanding is only the starting-point, but it is definitely a crucial step to guarantee the success of our daily decisions and actions in this global information-driven society.
Logic is a cornerstone of rational thinking. The attempt to base mathematics on logic led in the first part of the 20th Century to a foundational crisis in mathematics. The insight that came out of this crisis was that a mathematical proof is evidence that can be checked computationally. And thus was born computer science.
Logic plays an essential role in the modern world of information; but that is a distraction. The study of Logic leads not to easy technical answers but to hard questions about meaning which lie behind all our attempts at understanding.

Vienna Logic Day Lecture

Computer Science is the continuation of Logic by other means. – Georg Gottlob

The first Vienna Logic Day Lecture at VCLA is an free online event which offers the possibility to participate from all over the world.

Date: January 14, 2021

Time: 8am PST | 11am EST | 1pm GMT-3 | 5pm CET (Vienna)

We are very excited to announce the speaker of the 1st Vienna Logic Day Lecture 2021:

Prof. Georg Gottlob
(University of Oxford, TU Wien)

Title: Knowledge Processing, Logic, and the Future of AI

Thinking, Fast and Slow, machine version? Prof. Gottlob discusses advances in interaction between logical reasoning and machine learning leading to fair automated decision-making.

LOGIC events around the world

List of events celebrating World Logic Day 2021 on 14 January 2021.*

If you are organising an event and wish to be listed in the official list of the World Logic Day 2021 events and use the official WLD logo in your announcements, please visit the website of the WLD 2021. To be included on the event list on this website, please send us an email.

*The events which take place outside the designated day (Jan 14) will be featured with their date instead of the time.

**Events are taking place virtually.


Jan 13-15

9:00 CET

12:00 CET

13:00 CET

13:00 CET

15:00 CET

15:30 CET

17:00 CET

17:00 CET

18:00 CET

19:00 CET

23:00 CET


Jan 14-15

Jan 15

Jan 15

Jan 16


Peru – Peruvian Society for Epistemology and Logic: Luis F. B. Alegre

Spain – Group for logic, language and information at U. Sevilla: Cristina B. Gómez

Croatia – Croatian Logic Association: Srećko Kovač

Russia – Sobolev Institute of Mathematics: Nikolay Bazhenov and Manat Mustafa

Kazakhstan – Nazarbayev University: Nikolay Bazhenov and Manat Mustafa

Italy – Italian Association for Logic and Applications, SILFS, EATCS: Silvio Ghilardi

Austria – Central European University: Hanoch Ben-Yami

Austria – TU Wien: Agata Ciabattoni, Stefan Szeider

Italy – SILFS, ALOPHIS, U. OF CAGLIARI: Francesco Paoli, Giuntini Roberto 

Germany – University of Konstanz: Deborah Kant, Deniz Sarikaya

USA – Rice University: Moshe Vardi

Mexico: Gabrielle R. García (UNAM), María R. M.Ordaz (UFRJ), Cristian A. G. Ramirez (UNAM)

Germany – FernUniversität in Hagen: Claudia Anger, Jens Lemanski

Poland – Adam Mickiewicz University & U. of Lodz: Dorota Leszczyńska-Jasion

Germany – Universität Hamburg: Deniz Sarikaya

United Kingdom – Imperial College London: Alessandra Russo, Mark Law

Switzerland – ETH Zürich: Jose Perez Escobar, Deniz Sarikaya

Spread the logic

Social media constitute an important medium for disseminating information. We are not collecting statistics on the shared content, and are working with GDPR compliant plugins which do not follow you around the world wide web. Thus sharing this content on social media or in private communication is encouraged.

What social media need is more scientists –
not celebrity influencers. – S.Mojad in Science, Sep 2017

Scroll to top