Tribute to Egon Börger on the Occasion of his 60th Birthday

he got his doctoral degree and in 1976 his “Habilitation ” in mathematics. The themes of his doctoral dissertation, Reduction classes in Krom and Horn formu-lae, and of his “Habilitationsschrift, ” A simple method for determining the degree of unsolvability of decision problems for combinatorial systems, have their root in the computational view of mathematical logic held at the time at the Institute for Logic and Foundations of Mathematics at the University of Münster, a tra-dition going back to (among others) Leibniz, Ackermann, Gödel, Post, Turing, Kleene, and associated in Münster with the names of the founder of the insti-tute, Heinrich Scholz, and his followers Hans Hermes, Gisbert Hasenjäger and Dieter Rödding. This heritage determined the focus of Börger’s logical investi-gations in what nowadays is called computability and computational complexity theory and his early interest in applying methods from logic to solve problems in computer science. Thus, it does not come as a surprise that from 1972 to 1976 Börger followe