David Finkelstein died February 23, 2016 at the age of 86. He was one of the most original thinker in the basic structures of quantum theory and relativity. His main aim, especially in the last twenty years of his life, was to find a bridge, or to explain a connection, between the epistemological structure of our thinking and the basic structures of the physical nature. The originality and the width of his ideas shines up in the contributions of his scientific and personal friends and partners in this special issue of the International Journal of Theoretical Physics whereof he was the editor-in-chief for many decades. This special issue includes David Finkelstein’s last “work in progress”, Unitary Quantum Relativity, with the date November 19, 2015 as found in David’s computer.