Egon B.. orger Tribute to Egon B.. orger on th the Occasion of his 60 Birthday 1 2 Jean-Raymond Abrial and Uwe Glasser .. 1 jrabrial@neuf. fr 2 glaesser@cs. sfu. ca Egon B.. orger was born on May 13, 1946, in Westfalia (Germany). After the cl- sic baccalaur' eat, from 1965-1971 he studied philosophy, logic and mathematics at the Sorbonne (Paris, France), Institut Sup' erieur de Philosophie de Louvain (Belgium), Universit' e de Louvain and Universitat .. Munster .. (Germany), where he got his doctoral degree and in 1976 his "Habilitation" in mathematics. The themes of his doctoral dissertation,ReductionclassesinKromandHornfor- lae,andofhis"Habilitationsschrift,"Asimple method for determining thedegree of unsolvability of decision problems for combinatorial systems,havetheirroot inthe computationalviewofmathematicallogicheldatthe time atthe Institute for Logic and Foundations of Mathematics at the University of Mu ..nster, a t- dition going back to (among others) Leibniz, Ackermann, G.. odel, Post, Turing, Kleene, and associated in Munster .. with the names of the founder of the ins- tute, Heinrich Scholz, and his followers Hans Hermes, Gisbert Hasenj. ager and Dieter R.. odding. This heritage determined the focus of B.. orger's logical inves- gations in what nowadaysis called computability and computationalcomplexity theory and his early interest in applying methods from logic to solve problems in computer science.