Operative Logic and Mathematics would appear to be a new venture. Only a few weeks before his premature death Hermann Weyl, one of the most original mathematicians of our time, the author of a Philosophy of Mathematics and Natural Science and also of a stimulating book on Symmetry, drew my attention to Paul Lorenzen's Einführung in die operative Logik und Mathematik(Springer, Berlin). This book had given him new hope, since GÖdel had discouraged his endeavour to find the foundations of mathematics. “Perhaps,” he added, “Lorenzen's approach promises a way of arriving at reliable foundations.”