Aleksander Peczenik unexpectedly died in 2005 at the age of 68. At that time, he was still very active both as the chairman of the IVR (International Association for Philosophy of Law and Social Philosophy) and as a scientist. During his prolific scientific career, Peczenik wrote several books, and it is a hazardous enterprise to pick out one of them as the most important one. If this hazardous enterprise needs to be undertaken, however, On Law and Reason would be a responsible choice. In this book Peczenik has tried to bring together many strands of his thought on the nature of legal justification and on the nature.
