Memorial page for Petr Hájek

* 6. 2. 1940 + 26. 12. 2016

Petr Hájek was a renowned Czech mathematical logician with a professional record that spans more than half a century. His work leaves a permanent imprint in all of his research areas: set theory, arithmetic, fuzzy logic and reasoning under uncertainty, and information retrieval; some of his results enjoyed successful applications. Throughout his career, he worked at the Czech Academy of Sciences, starting as a postgraduate student at the Institute of Mathematics in 1962. During 1992-2000, he served as director of the Institute of Computer Science; he eventually became an emeritus scholar of the Academy.

Petr Hájek (co-)authored seven books, more than 350 research papers, textbooks and popular articles; his works are frequently cited with the number of citations amounting to 3000. He taught logic at the Faculty of Mathematics and Physics, Charles University in Prague, where he was appointed full professor in 1997, and at the Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University. He also taught at the Vienna University of Technology, where he was appointed honorary professor in 1994. For the timespan of four decades, he would run a weekly seminar of applied mathematical logic, and he co-founded another seminar on mathematical logic at the Institute of Mathematics.

He served as a member of committees and editorial boards and was a long-time member of the Union of Czech Mathematicians and Physicists. From 1993 he was a member of the Association for Symbolic Logic. During 1999 to 2003, and 2009 to 2015, he was the President of Kurt Gödel Society. From 1996 he was a member of the Learned Society of the Czech Republic. During 1993 to 2005 he was a member of the Scientific Council of the Academy of Sciences of the Czech Republic. His awards include the Bolzano medal from the Academy of Sciences in 2000, a medal of the Minister of Education of the Czech Republic in 2002, the „De scientiae et humanitate optime meritis“ medal from the Academy of Sciences in 2006, the Medal of Merit from the President of the Czech Republic in 2006, and the Josef Hlávka medal in 2009.

Apart from the pursuit of mathematics, Petr Hájek was an organist. He graduated from the Academy of Performing Arts in Prague and was, for a considerable period of time, organist on Sundays at the protestant St. Clemens Church in Prague; since childhood years he was a member of the Evangelical Church of Czech Brethren.

Petr Hájek was married, with two children and a grandson. He was fluent in several languages, including German, English, and Polish. Generally appreciated as a friendly and modest person, known for his readiness to help and listen to others, many colleagues considered him their teacher and mentor. He was respected for his principles, not least among these, his stands during the communist era, when he would not enter the communist party nor cooperate with the state security when asked to. For that reason, for considerable periods of time he had been prevented from advancing his career or travelling abroad.

Petr Hájek will be remembered by his colleagues, friends and students across continents for his contributions to mathematical logic and for his friendliness, honesty, and fortitude.

The list of published works of Petr Hájek, maintained by the Library of the Institute of Computer Science, is available at

See also the memorial page on the CAS website:

Condolence messages can be sent to or privately to his family to

Condolence messages

When I read the news, I recalled many warm memories of moments with Petr. He was present at the very beginning of my mathematical endeavors. As a student, I participated in his logic seminar on Monday mornings. (Monday is important here: in those old times with no central heating Petr used to arrive to his office very early, so that he personally could set and light a small coal stove, to make the office cozy after cold winter weekends.) I also remember the remarkable (theo)logical debates on the topic of Gödel’s proof of the existence of God led by Petr Hájek together with Petr Vopěnka and Antonín Sochor (who both have passed away some time ago) – and many other professional and personal encounters. I am glad I could get to know Petr and meet him again and again. He is one of the people who enriched my life tremendously.

Jiří Sgall

Vážení kolegové,

přijměte prosím hlubokou a upřímnou soustrast. Smrt prof. Hájka je velká ztráta pro českou matematiku. Prof. Hájek měl k ÚTIA velmi blízký vztah a řada z nás ho považovala za svého učitele.

Jan Flusser

The Family of Prof Petr Hajek,

My Dears,

It is with great sorrow that we lost our eminent great logician. When Prof Gottwald described his contribution as: “a mine of gold”, this was an
understatement. His monograph: “The Metamathematics of Fuzzy Logic” was indeed as the *Begriffsschrift* of Gottlob Frege for us. Indeed
establishing: “Mathematical Fuzzy Logic” as a legitimate branch of Mathematical Logic.

When the Fuzzy Logic community won Prof Hajek, it was like the Quantum Mechanics community won John von Neumann in the early 20th century.
May his soul rest in peace together with Aristotle.

My condolences,

Rafee Kamouna

Please accept my most sincere condolences. Petr Hájek will be remembered and honoured not only for his qualities as a preeminent scientist and a teacher, but also for the warmth and strength of his character making every meeting with him a real privilege for the rest of us.

Jiří Zlatuška

Prajem uprimnu sustrast vsetkym, co ho mali radi. Nebol len vynikajuci vedec, ale v prvom rade vzacny clovek.


Juraj Hromkovic

Velmi rád bych vyjádřil soustrast Vám pane řediteli, pozůstalým i kolegyním a kolegům v souvislosti s úmrtím pana profesora Petra Hájka.
Pana profesora jsme dobře znali i za mého působení ve Filosofickém ústavu a velmi si vážili jeho odborných i lidských kvalit.

Se srdečným pozdravem,

Pavel Baran

Vazeny pan riaditel,

s hlbokym zarmutkom sme prijali spravu, ze zomrel Petr Hajek, popredny cesky matematik svetovej povesti. Profesor Hajek bol spolupracovnikom mnohych slovenskych matematikov, osobne spominam na jeho seminare z logiky v sedemdesiatych rokoch. S laskou spominame na vynikajuceho matematika a dobreho cloveka.

Karol Nemoga

Vážený pane řediteli,

přijměte moji upřímnou soustrast nad ztrátou Vašeho kolegy. Jeho odchodem ztrácí česká matematika významného odborníka a organizátora. Prof. RNDr. Petr Hájek, DrSc. byl dlouholetý spolupracovník Katedry matematiky FJFI. Svým působením výrazně přispěl k rozvoji oboru Matematické inženýrství, a to jak přednáškami předmětu Fuzzy logika, tak i výchovou magisterských studentů a doktorandů. Dnes na katedře působí jeho žáci. I proto věříme, že nadšení pro matematiku, které z profesora Hájka vždy vyzařovalo, bude na katedře přítomno i nadále.

prof. Ing. Igor Jex, DrSc.

Vážený pane řediteli,

přijměte, prosím, Vy i celý kolektiv Vašeho ústavu mou hlubokou soustrast nad odchodem profesora Hájka. Jako bývalý vedoucí katedry matematiky FJFI ČVUT mohu jen potvrdit slova děkana fakulty profesora Jexe. Odešel významný matematik a velký člověk. Čest jeho památce.

Jan Mareš

Dear Sirs,

One of the things that I thank life for has been the opportunity to meet Dr. Petr Hájek.
I had the privilege of being his PhD student, and the immense honor of having a friendship with him that went beyond distance and time.
He was a brilliant scientist and the deepest intelligence I have ever known. What made him even more exceptional were his great human dimension and his immense and kind heart.
With him, Science lost one of its brightest minds. I lost my friend and mentor.


Julio J. Valdés
National Research Council Canada

I have been deeply grieved to learn of the death of Petr Hájek and I send my deepest sympathy to his family and friends. Petr Hájek will be long remembered as one who devoted his life to science and to the service of mankind. He highly supported the foundation and further development of medical informatics research at the Institute of Computer Science and he was cooperating with me in several medical informatics projects. I shall always regard it as an honor and a privilege to have known him personally.

Jana Zvárová

Milý Petře,

mnohé skutky Tvého života budou jistě uznány za spravedlivé, a mnoho z toho, co jsi prožil a udělal, je veliké i v lidských očích. Jsem vděčný za to, že jsem mohl jít kousek cesty nedaleko.

Zdeněk Strakoš