TbiLLC 2015: Eleventh International Tbilisi Symposium
on Language, Logic and Computation

Honorary doctorate Dick de Jongh and Matthias Baaz


Prof. Dick de Jongh (ILLC, University of Amsterdam) and Prof. Matthias Baaz (Vienna University of Technology) were awarded honorary doctorates of the Ivane Javakhishvili Tbilisi State University.

The ceremony was held during The Eleventh Tbilisi Symposium on Logic, Language and Computation, Tbilisi, Georgia, 25 September, 2015.




Opening speech, David Gabelaia

Ladies and Gentlemen,

We are here today to pay tribute to two distinguished scholars in the field of Mathematical Logic – Professors Dick de Jongh and Matthias Baaz. It is a lucky coincidence that this celebration is held during the eleventh International Tbilisi Symposium on Logic, Language and Information and just a week after the eleventh International Tbilisi Summer School in Logic and Language.  Being a regular participant and lately one of the organizers of these events, I must put aside modesty in declaring that these are two of the most successful regular international science events in Georgia. The audience in this room today is a witness to this fact, being composed of leading researchers and professors from all over the world, including Georgia. Without even slight exaggeration, the success, quality and incessant regularity of these events is largely due to the efforts of my esteemed colleagues, professor Dick de Jongh and professor Matthias Baaz.


It is with great pleasure that I find myself today at the official recognition of their outstanding contribution by my Alma Mater, Ivane Javakhishvili Tbilisi State University. Without delaying you further, let me commence the ceremony by passing the word to the Rector of the University, member of the Georgian Academy of Sciences, Professor Vladimer Papava.

Vladimer Papava

Honourable guests,
Ladies and Gentlemen,

Allow me to greet you on behalf of Ivane Javakhishvili Tbilisi State University, which hosts today two world-renown scientists: professor of the Institute for Logic, Language and Computation of the Amsterdam University, Dr. Dick Herman Jacobus de Jongh and professor of the Vienna University of Technology, the chairman of the Kurt Gödel Society, Dr. Matthias Baaz. The Georgian schools of linguistics, logic and mathematics have a long-standing tradition of high quality research. This tradition continues to this day, with a formidable contribution of Professors Dick de Jongh and Matthias Baaz. For almost twenty years now, they have been selflessly striving to advance the knowledge of Georgian students.
In particular, with the financial and scientific support of the Amsterdam University, biennially since 1995, Georgia hosts International  Symposia on Logic, Language and Computation. During these symposia, established scientists from all over the world give tutorials and invited lectures for Georgian students.

Starting from 2004, each year this university hosts the Summer School in Logic and Language organized and supported entirely by Kurt Godel Society and Vienna University of Technology.
With the support of Matthias Baaz and Dick de Jongh several joint research projects have taken place, the English-Georgian journal “Language, Logic, Computation” is published regularly and many of the Georgian students were given the opportunity to obtain Master’s and PhD degrees in Austria, the Netherlands and elsewhere.



Many of these students continue their successful scientific career in leading institutions around the world, while some returned to Georgia and continue the strong tradition of linguistics and logic in this country.

And now, let me read the decision of the Academic Council of the Ivane Javakhishvili Tbilisi State University.



D. G.
And now, after this beautiful ceremony, I would like to give floor to the renowned Georgian linguist, member and former president of the Georgian Academy of Sciences, Professor Thamaz Gamkrelidze.

Thamaz Gamkrelidze

Esteemed Colleagues, Dear guests,
It is a great pleasure to be present at this event. I would like to say a few words about the honorary doctors of the Ivane Javakhishvili State University, Dick de Jongh and Matthias Baaz.
Dick de Jongh received his Bachelors in Mathematics and Physics from the University of Leiden in 1961. He then moved to Amsterdam to do his Master's under the supervision of Professor Beth.

Amsterdam of those days with Professors Brouwer, Heyting, Beth and young talented students such as Anne Troelstra and Dick de Jongh was one of the places where modern logic was born. Already back then Dick de Jongh got fascinated by the ideas of intuitionistic logic and he kept this interest until today. As master students Dick de Jongh and Anne Troelstra wrote a paper on duality for finite Heyting algebras which is a finitary version of the duality theory developed by Leo Esakia in Georgia a few years later. Thus, without realizing it, Dick already then was building bridges between the Dutch and Georgian logic schools.
After completing his Master's in 1964 Dick de Jongh moved to Madison, Wisconsin to do a PhD under the supervision of Professor Stephen Kleene who was one of the founders of recursion theory - a major branch of mathematical logic nowadays. There de Jongh proved a characterization of intuitionistic logic via the Kleene slash which is nowadays called the de Jongh characterization.

Dick de Jongh completed his PhD in 1968, returned to the Netherlands and joined the University of Amsterdam where he has been working since, first as an assistant professor and later as a full professor (the chair once held by Brouwer, Heyting, and Troelstra).
Dick de Jongh has been extremely productive during these years. Many landmark results in the area of intuitionistic and modal logic bear his name, for example the de Jongh-Sambin fixed point theorem in provability logic.

Dick supervised many Master and PhD students among which Nick Arevadze and Nick Bezhanishvili - more Georgian connections! Together with his colleagues Dick established the ILLC, the Institute for Logic, Language and Computation, which is by now one of the most celebrated centers of logic and linguistics worldwide with its landmark Master of Logic programme whose first director was Dick de Jongh.

Dick de Jongh has also been the driving force behind the success of Tbilisi Symposia - the wonderful interdisciplinary conference bringing together leading international researchers working on the interface of logic, mathematics, linguistics and computer science. Dick stood by the Georgian logicians and linguists in the most difficult times during the economic crisis of the 90's and to a large part it is his merit that the Tbilisi symposia have been flourishing and have become a major event in this area.

Professor Matthias Baaz is a world-renown expert in Proof Theory and Automated Deduction and the chairman of Kurt Goedel Society. One can say that he is the heir of the great logical tradition of Vienna. He was educated in Vienna, first at the University of Vienna and then at the Vienna University of Technology, where to this day he remains as a professor at the Institute of Discrete Mathematics and Geometry and head of the research group on Mathematical Logic. He made significant advances in the fields of Proof Theory, Automated Deduction and Many-valued Logic. Some focal points of his research are Goedel Logic, Cut-elimination, Skolemization and Interpolation. He is an author of well over 100 scientific publications mostly in the top journals and conference proceedings of the field.

Professor Baaz is an active researcher with a large network of collaborations all across the world, notably France, Italy, Spain, Russia, Israel, USA, Japan, Canada and Georgia. Many of the younger generation of logicians have benefited from working in his research circle. These include Agata Ciabattoni, George Metcalfe, Rosalie Iemhoff, Norbert Preining, Richard Zach, Arnold Beckmann and Mikheil Rukhaia.

He has organized or stood in the committees of many important scientific events. Most notably perhaps, he was the main scientific figure behind the "Vienna Summer of Logic" organized in 2014 - the largest event in the history of logic counting over 2500 participants in 12 major conferences and many dozens of workshops. For certain, this event will remain a major milestone in the history of mathematical logic.

In his capacity as the chairman of the Goedel Society, Matthias Baaz is one of the founders of the prestigious Goedel Centenary Research Prize Fellowship.

Last but not least, Professor Baaz has devoted considerable amount of his energy to providing scientific and financial support to the Georgian community of logicians, amongst other things, single-handedly organizing the yearly Summer Schools at this very university to the benefit of the younger generations of Georgian logicians.

It is with sincere joy that I congratulate my highly esteemed colleagues Dick de Jongh and Matthias Baaz upon the reception of the honorary degree of the Tbilisi State University. It is a well-deserved recognition of their great contributions to science in general and to maintaining high standards of the Georgian linguistics and logic schools in particular.


Next to speak is a scientific descendant of Professor de Jongh, Assistant Professor at Institute for Logic, Language and Computation, University of Amsterdam, my dear friend Nick Bezhanishvili.

Nick Bezhanishvili


Ladies and Gentlemen,

Professor Gamkrelidze already discussed the scientific achievements of Dick and Matthias. I would like to add a couple of words about my personal encounters with them. I was lucky to be Dick de Jongh's PhD student and to have many opportunities to interact with Matthias Baaz.

I moved from Georgia to Amsterdam in the winter of 2002. This wasn't easy for me in the beginning. As you can guess, I was spoiled by Georgian food, good weather and warm social atmosphere. Also we had Leo Esakia the founder of the Georgian logic school who raised a few generations of Georgian logicians. Leo was a fatherly figure to many of us (David and myself included) and his landmark seminars that would last for many hours were something that we all loved. Sadly, Leo is not here with us any more. He passed away in 2010, but we are happy to have Mrs Esakia here whom I would like to greet warmly.


However, thanks to Dick (and of course other people at the ILLC) my adaptation to Amsterdam and the academic life there was very smooth. Dick and I would often meet and discuss various research topics for hours sometimes over weekends. We continuou doing this till this day. This very much resembled the seminars that we had in Georgia. So very soon I felt being very much at home in Amsterdam.

In fact, it was not a coincidence that our collaboration went well. Dick loves working with junior colleagues and students. He treats them as equals but also pushes them to excel.
We've got examples of this at this conference. Dick's talk at this conference was co-authored by two young Master of Logic students from Amsterdam Ana Lucia Vargas and Almudena Colacito. Apostolos Tzimoulis and Zhiguang Zhao (PhD candidates at TU Delft) here had a talk co-authored by Dick on a project supervised by him. Julia Ilin (PhD candidate at ILLC) and Dick just finished a joint paper. Aybuke Özgün (PhD candidate at Loria, Nancy and ILLC) was strongly supported by Dick to study at the Master of Logic programme and he also connected her and me for doing a project together.

In 2009 we had a satellite workshop of the Tbilisi Symposium dedicated to Dick de Jongh and Leo Esakia. I was absolutely delighted by this since this was a real celebration of the work and life of two outstanding researchers that had profound effect on me as a researcher and person.


Some of you may know that Dick is also a committed cyclist and even a member of the committee of Amsterdam city hall that is in charge of organizing bike lanes in the city. In fact, when I was a PhD student in Amsterdam, my favourite cycling route to the university would go through a wide street along the Amstel river that was especially designed for cyclists and where cars were banned. Only later I learned that it was Dick and this committee that fought very hard with city hall to negotiate this path. Unfortunately, we do not have such a committee and such enthusiastic members in Tbilisi yet. Hopefully we will have them in some not very distant future...

Also Dick himself is a very skilled cyclist. It was always embarrassing for me to cycle with Dick since I was always behind him no matter how hard I tried.


The first time I've met Matthias was at one of the Tbilisi Symposia. I was at a lunch table where Matthias was discussing politics with someone. He was providing such an interesting analysis that I just couldn't stop listening. I had a pleasure of having many other interesting discussions with Matthias about politics and I can reassure you that all his predictions always come true in one way or another. And btw if you want to learn things about Georgian politics or history please consult Matthias and he will explain to you all the details in a very simple and truthful way. It's also a pleasure to hear Matthias' numerous anecdotes about various famous logicians.


Matthias is also a person that always has a solution to any complex situation. He always uses his calm but affirmative style and I personally seen him resolving many critical issues related to the Tbilisi Symposia in this way.


Matthias and Dick are "Georgian" in many ways. Some of it we have already experienced at this Symposium. We have seen that Dick is a great dancer and Matthias is a great tamada (toast master). Above all Dick and Matthias are great researchers with deep insights. It's always a pleasure and indeed a privilege to interact with them and to hear their interesting ideas.

I would also like to greet Dick and Matthias's wonderful spouses Christel and Nino. Nino is here now. She is the soul of the Tbilisi-Vienna school and without her titanic efforts that event would have never come to life. Christel is unfortunately not here, although she has visited Georgia a number of times. My friends often ask me how come I am so up-to date about new Georgian movies. Well, the reason is that Christel often organizes Georgian movie nights in Amsterdam when we go to a cinema and watch new Georgian releases. Christel and Nino have been great supporters and sources of inspiration for Dick and Matthias.

Dear Dick and Mathias, many congratulations on this well deserved honor and best of luck in the future which, I am sure, will be connected to Georgia!



Dick de Jongh

Highly esteemed rector,

esteemed ladies and gentlemen,

It is a great honor for me to stand here to receive such a high distinction from this venerable university. My conviction is that in the first place are hereby honored, (1) the Tbilisi Symposium and (2) the Georgian school of logic. The Tbilisi Symposium is just now being held for the 11th time. I first attended this biannual Symposium in its second edition in 1997 and have attended it each time since.


The reason that I and others attended that first time was the fact that it was announced as a Symposium on Logic, Language and Information. This goes right along with the philosophy of my institute, the ILLC, the Institute of Logic, Language and Computation which holds that logic doesn't stop at the borderlines of pure mathematical logic but is at the center of an area of intermingling interdisciplinary studies in the areas of at least philosophy, linguistics, computer science and cognitive science. This philosophy was instilled in me personally not by the ILLC but long before its existence by my teacher E.W. Beth. It is by no means a truth that is recognized everywhere and I was happy to see that the Center of Logic, Language and Speech, the Institute of Mathematics of Tbilisi State University and the Georgia Academy of Sciences who co-organized this symposium really supported the same cause. The Symposium was organized with great enthusiasm, I would like to mention the names of George Chikoidze, Rusiko Asatiani, Marina Ivanishvili, Nani Chanishvili. Moreover, it had a program with outstanding foreign visitors. At the time the country had greatly suffered from a civil war, conditions were such that organizing such a conference had been very
difficult, and it was clear that assistance to the organizers from a like-minded institute would be very helpful. This meant the start of a long and continuing cooperation with these organizers, the ILLC has since then been part of the organization of this Symposium, a cooperation that has been beneficial to both partners.

When I arrived that first time I knew that an eminent logician Leo Esakia had been doing work in an area closely related to my own. What I didn't know and could see now with my own eyes was that he was the leader of a very strong group working in algebraic logic. What I also didn't realize was that a basis had been set on the philosophical side for many years by the logicians Lery Mchedlishvili and Mikheil Bezhanishvili. The latter had two sons one of which was already part of Leo Esakia's group and the other was soon to be. A cooperation between Leo Esakia's group and the ILLC was also set in motion. Some Georgian students, and not only mathematical logicians, joined the ILLC Master Program in Logic. One among those was David Gabelaia who at the present time is the local leader of the organization of the symposium. Later Nick Bezhanishvili came over as a PhD student to me, and a number of years after that he has joined the ILLC as an assistant professor.

In the meantime the eighth edition of the symposium was dedicated to the work of Leo Esakia and myself. Unexpectedly Leo died just a year later. But after this sad occurrence the cooperation between the ILLC and his group continued as a matter of course. This is so, even though its members are for a large part scattered over the world. The State University of Tbilisi may rightly be proud of this logic group and especially of the small section of it that works in Tbilisi itself. The great name that Tbilisi has in logic deserves all the support the University can give it, and any support such a group gets will benefit the university itself many times over.
To return to what I said in the beginning, I consider the honor I receive with deep gratitude as really bestowed on all the people with whom I have worked in this common enterprise. I thank all the people I have mentioned and many more. One person I have not yet mentioned and to whom I am very grateful as well is my colleague next to me, Mathias Baaz, who has all these years steadily worked with great persistence side to side with me with the same objectives in mind. To conclude, let us hope that the eleven symposia that have taken place are just the beginning of a really long tradition. Thank you.


David Gabelaia

Let me conclude this ceremony by some words of acknowledgement. I would like to thank, first of all, the researchers of the Insitute for Theoretical and Applied Linguistics at this university, professors Marine Ivanishvili and Rusudan Asatiani. It was their idea, and their unceasing energy that made today’s event possible. Being actively involved in the organization of Tbilisi Symposia and Vienna-Tbilisi Summer Schools, they, more than anybody else, know about the crucial role played by Professors de Jongh and Baaz in advancing Georgian science. I would also like to thank everyone at Tbilisi State University who helped us make this idea into the reality we are witnessing today. Especially, I’d like to thank the Academic Council of the university and Dr. Mzekala Atchaidze, Georgian Academy of Sciences and Prof. Thamas Gamkrelidze, Department of exact Sciences and Prof. Revaz Grigolia, Razmadze Mathematical Institute and Dr. Mamuka Jibladze, and finally, the Rector of Ivane Javakhishvili Tbilisi State University, Prof. Vladimer Papava. Please join me in acknowledging them.

With this, let me conclude this ceremony and invite you all to the less official, but no less important celebration to be held tonight. Thank you.