While we are here to honor a Man of Science, and I will soon sketch why, I first want to observe that his dedication to the scientific enterprize has been faithfully supported by the love of an ever increasing family, and that his intellectual elegance is inseparable from his roots in a City of intense culture.

Walter Thirring was born in Vienna; twice, and twice from the same father. Firstly, he came to material existence there in 1927; and secondly, Hans Thirring, Professor of theoretical Physics at the University of Vienna, directed the research that led to the Doktor Phil. degree Walter completed in 1949 at the tender age of 22.

A ten-year Wanderlust followed, during which Walter Thirring had various positions at: the Institute of Advanced Studies in Dublin, the University of Glasgow, the Max-Planck Institute in Goettingen, the Federal Institute of Technology in Zurich, the University of Bern, the Institute for Advanced Study in Princeton, Bern again, the Massachusetts Institute of Technology, the University of Washington at Seattle, and Bern once more. Take heart, you budding Mathematical Physicists in the audience, graduate students and postdoctoral fellows: these, like ours, were times when securing a permanent job required fortitude.

In 1952, Walter Thirring married Helga Georgiades, whom I am pleased to salute in the first rank of this audience. Klaus and Peter were born from this union, and they provided the Thirrings with four grandchildren, the last two twins born this Spring.

In fact, Walter Thirring's family extends much further, as he is more than a ``Doktorvater'' to his doctoral students, not only during their official formative years, but well beyond. I tried to count their number; I found anywhere between fifteen and sixty of them ... depending of the algorithm I used. Indeed, Walter succeeded in creating at the Institute for Theoretical Physics a truely cooperative team, a true institute for theoretical physicists. I met many of these former students, had enlightening discussions with several of them, and worked on papers with some; never did I hear from them anything but the kind of praise and gratitude that prevail in a vibrant family. Being admitted to share their bliss was one of the greatest scientific joy of my professional life.

Let us now return to Walter Thirring's own scientific career which we left in 1959. He then became o.Univ.--Professor in Vienna, a position in which he remained until he became Emeritus in 1997, except from an interlude from 1968 to 1971 when he was a Member of the Directorate at CERN in Geneva. The latter experience served us all well when, in the tumultuous 1970s, he became the first President of the AMP, soon to become our International Association of Mathematical Physics, which he contributed to set as the open international forum his successors have maintained. It is true that we now have by-laws and traditions; they allowed us to survive a tenfold increase in membership from the founding days several of us in the audience remember.

Walter Thirring's administrative talents have always been guided by an acute sense of responsability not only to Science, but also to its practitioners. For instance, in 1993, he became the founding Director of the Erwin Schrödinger Institute which he initiated as a response to the debacle that followed the fall of the iron curtain: East and West now meet again in Vienna. It is an amusing coincidence that the new quarters of the Institute are located in the former Priesterseminar. If science is still a sacerdoce that knows no national frontiers, you find this spirit alive and well at ESI.

All the above however should not make us forget that Walter Thirring is first and foremost an active scientist. He is the author of some 160 papers and several books, two of which I wish to mention here.

The first is the Lehrbuch der Mathematischen Physik, in four volumes, originally published by Springer-Verlag Wien, 1977-1980. Depending on the time when we individually came of age, we know them in several avatars. The less young among us knew them in their former incarnation as the ``grüne Hefte'', typed and mineographed pristine lecture notes; and the younger generation studied from the widely distributed and universally respected English translation, due to Evans M. Harrell.

The other book that must be mentioned here is the ``Selected Papers'' with commentaries, preceded by a foreword from Elliott Lieb. This came out under the aegis of the American Mathematical Society, Providence RI, 1998. Being a selection, they represent a choice among Walter Thirring's contributions to Mathematical Physics, Statistical Physics, Quantum Field Theory, General Relativity, and Elementary Particle Physics.

A third, and less known contribution Walter made to 20th-Century culture stemmed from his musical interests, the Suite bourbonnaise for organ. I know it only as a tape made during the premičre Walter gave of his composition commissionned by the Cathédrale de Moulins (France) on September 25, 1994. If you ever visit Walter's home, ask to listen to it. I should only say here that I am privileged to own a copy of this tape, and listen to it every time I want to remember the evenings when I enjoyed concerts of contemporary music in Vienna during the rare respites our collaboration gave me. Warning: Walter works hard and thinks concisely; his back-of-a-postage-stamp ciphers do deserve elaboration.

As I was preparing this presentation, I made my own personal choice among his papers to try and delineate those aspects of his genius that appeal most to me. I hope this list is also representative, and my conclusion is to offer it for your perusal. All (except the last two, evidently) happen to be included in the Selected Papers of Walter Thirring.

- #15. On the divergence of perturbation theory for quantized fields, Helv. Phys. Acta 26 (1953) 33-52
- #30. A soluble relativisitic field theory, Ann. of Phys. 3 (1958) 91-112
- #71. On the mathematical structure of the BCS model, Comm. Math. Phys. 4 (1967) 303-314 (with A. Wehrl)
- #94. Bound for the Kinetic Energy of Fermions which proves the stability of matter, Phys. Rev. Lett. 35 (1975) 687-689 (with E. H. Lieb)
- #108. A lower bound with the best possible constant for Coulomb Hamiltonians, Commun. Math. Phys. 79 (1981) 1-7
- #123. Dynamical entropy of C^*-algebras and von Neumann algebras, Commun. Math. Phys. 112 (1987) 691-719 (with A. Connes and H. Narnhofer)
- #151. Anosov actions on non-commutative algebras, J. Math. Phys. 35 (1994) 5582-5599 (with GGE, H. Narnhofer, and G.L. Sewell)
- #156. How hot is the de Sitter space? Int. J. Math. Phys. B10 (1996) 1507-1520 (with H. Narnhofer and I. Peter)
- #1xx. Equivalence of modular K- and Anosov dynamical systems, Rev. Math. Phys. 12 (2000) 445-459 (with H. Narnhofer)
- #1yy. The classical three-body problem -- Where is abstract mathematics, physical intuition, computational physics most powerful? (with H.A. Posch), in Mathematical Physics 2000 (A. Fokas, A. Grigoryan, T. Kibble and B. Zegarlinski, eds.) Imperial College Press, London 2000.

I am sure I express the hopes of all of us when I wish Walter Thirring the pleasure to continue to spend time at both the mathematical physics drawing board and the organ key board, for his enjoyment and ours.