Andrzej Mostowski was one of the leading 20th century logicians. His legacy is examined in this volume of papers devoted both to his extraordinary scientific heritage and to the memory of him as a great researcher, teacher, organizer of science and person. Professor Mostowski pioneered and mastered many areas of mathematical logic. His contributions spanned set theory, recursion theory, and model theory -- the backbone of the foundations of mathematics. The complete detailed bibliography of Mostowski's writings is included. For many years after WWII and especially in the late sixties and till his untimely death in 1975, Warsaw, where he led the centre of foundational studies, was a place where many leading logicians visited, studied, and started their career. Their memories form an important part of this volume, attempting to bring back the extraordinary achievements and personality of Mostowski. Anyone wanting to see the roots of current applications of logic, be it in mathematics, computer science or philosophy, will find in this collection of articles plenty of helpful, stimulating and inspiring material both in science and about the social environment in which science is made.