This volume is published in Honor of PhilipWadler on the occasion of his 60th birthday, and the collection of papers forma Festschrift for him. The contributions are made by some of the many who knowPhil and have been influenced by him. The research papers included hererepresent some of the areas in which Phil has been active, and the editorsthank their colleagues for agreeing to contribute to this Festschrift. We attemptto summarize Phil Wadler's scientific achievements. In addition, we describethe personal style and enthusiasm that Phil has brought to the subject.

Reactions on Monadic Lenses.- Conation ConfersConcurrency.- Counting Successes: Effects and Transformations for Non-deterministicPrograms.- The Essence of Inheritance.- Subtyping Supports Safe Session Substitution.Proof Relevant Parametricity.- Comprehending Ringads.- Dragging Proofs out ofPictures.- Experiences with QuickCheck: Testing the Hard Stuff and StayingSane.- Cutting out Continuations.- The Lambda Calculus: Practice andPrinciple.- I Got Plenty o' Nuttin'.- Pointlessness Is Better than Listlessness.The Essence of Dependent Object Types.- Linear lambda-mu Is CP (more or less).A Reaction on types.- The Essence of Multi-Stage Evaluation in LMS.- 1ML withSpecial Effects.- The Computer Scientist Nightmare.- A Branding Strategy forBusiness Types.- The Recursive Union of Some Gradual Types.- A Delta for HybridType Checking.- Certifying Data in Multiparty Session Types.- Recursion Equationsas a Programming Language.