Preface
In Memoriam: Grigori Mints
Part I: Reflections
1. Reinhard Kahle: Gentzen's Consistency Proof in Context
2. Michael Detlefsen: Gentzen's Anti-Formalist Views
3. Anton Setzer: The Use of Trustworthy Principles in a Revised Hilbert's Program
Part II: Gentzen's Consistency Proof
4. Wilfried Buchholz: On Gentzen's first consistency proof for arithmetic
5. Jan von Plato: From \emph{Hauptsatz} to \emph{Hilfssatz} (with an appendix by Siders/von Plato)
6. Dag Prawitz: Extending Gentzen's 2nd consistency proof to normalization of natural deductions in 1st order arithmetic
7. Annika Siders: A Direct Gentzen-style Consistency Proof for Heyting Arithmetic
8. W. W. Tait: Gentzen's original consistency proof and the Bar Theorem
Part III: Results
9. Sam Buss: Cut Elimination \emph{In Situ}
10. Fernando Ferreira: Spector's proof of the consistency of analysis
11. Herman Jervell: Climbing Mount $\varepsilon_0$
12. Wolfram Pohlers: Semi-formal calculi and their applications
Part IV: Developments
13. Toshiyasu Arai: Proof Theory for Theories of Ordinals III: $\Pi_{N}$-Reflection
14. Gerhard Jäger and Dieter Probst: A proof-theoretic analysis of theories for stratified inductive definitions
15. Frederik Meskens and Andreas Weiermann: Classifying phase transition thresholds for Goodstein sequences and Hydra games
16. Grigori Mints: Non-Deterministic Epsilon Substitution Method for $\mathsf{PA}$ and $\mathsf{ID}_1$
17. Paulo Oliva and Thomas Powell: A Game-Theoretic Computational Interpretation of Proofs in Classical Analysis
18. Michael Rathjen and Pedro Francisco Valencia Vizcaíno: Well ordering principles and Bar induction.