This volume is dedicated to Prof. Dag Prawitz and his outstanding contributions to
philosophical and mathematical logic. Prawitz's eminent contributions to structural proof
theory-or general proof theory as he calls it and inference-based meaning theories have been
extremely influential in the development of modern proof-theory and anti-realistic semantics.
In particular Prawitz is the main author on natural deduction in addition to Gerhard Gentzen
who defined natural deduction in his PhD thesis published in 1934. The book opens with an
introductory paper that surveys Prawitz's numerous contributions to proof theory and
proof-theoretic semantics and puts his work into a somewhat broader perspective both
historically and systematically. Chapters include either in-depth studies of certain aspects of
Dag Prawitz's work or address open research problems that are concerned with core issues in
structural proof theory and range from philosophical essays to papers of a mathematical nature.
Investigations into the necessity of thought and the theory of grounds and computational
justifications as well as an examination of Prawitz's conception of the validity of inferences
in the light of three dogmas of proof-theoretic semantics are included. More formal papers deal
with the constructive behaviour of fragments of classical logic and fragments of the modal
logic S4 among other topics. In addition there are chapters about inversion principles
normalization of proofs and the notion of proof-theoretic harmony and other areas of a more
mathematical persuasion. Dag Prawitz also writes a chapter in which he explains his current
views on the epistemic dimension of proofs and addresses the question why some inferences
succeed in conferring evidence on their conclusions when applied to premises for which one
already possesses evidence.
