This is a comprehensive book on the life and works of Leon Henkin (19212006), an extraordinary scientist and excellent teacher whose writings became influential right from the beginning of his career with his doctoral thesis on The completeness of formal systems under the direction of Alonzo Church. Upon the invitation of Alfred Tarski, Henkin joined the Group in Logic and the Methodology of Science in the Department of Mathematics at the University of California Berkeley in 1953. He stayed with the group until his retirement in 1991. This edited volume includes both foundational material and a logic perspective. Algebraic logic, model theory, type theory, completeness theorems, philosophical and foundational studies are among the topics covered, as well as mathematical education. The work discusses Henkins intellectual development, his relation to his predecessors and contemporaries and his impact on the recent development of mathematical logic. It offers a valuable reference work for researchers and students in the fields of philosophy, mathematics and computer science.

Part I Biographical Studies.- Leon Henkin.- Lessons from Leon.- Tracing back Logic in Wonderland to my work with Leon Henkin.- Henkin and the Suit.- A Fortuitous Year with Leon Henkin.- Leon Henkin and a Life of Service.- Part II Henkins Contribution to XX Century Logic.- Leon Henkin and Cylindric Algebras.- A Bit of History Related to Logic Based on Equality.- Pairing Logical and Pedagogical Foundations for the Theory of Positive Rational Numbers. Henkins unfinished work.- Leon Henkin the Reviewer.- Henkins Theorem in Textbooks.- Henkin on Completeness.- Part III Extensions and Perspectives in Henkins Work.- The Countable Henkin Principle.- Reflections on a Theorem of Henkin.- Henkins Completeness Proof and Glivenkos Theorem.- From Classical to Fuzzy Type Theory.- The Henkin Sentence.- April the 19th.- Henkin and Hybrid Logic.- Changing a Semantics: Oportunism or Courage?.- Appendix Curriculum Vitae: Leon Henkin.