This edited volume features essays written in honor of Ernst Mach. It explores his life, work, and legacy. Readers will gain a better understanding of this natural scientist and scholar who made major contributions to physics, the philosophy of science, and physiological psychology. The essays offer a critical inventory of Mach’s lifework in line with state-of-the-art research and historiography. It begins with physics, where he paved the way for Einstein’s Theory of Relativity. The account continues with Mach's contributions in biology, psychology, and physiology pioneering with an empiricist and gestalthaft Analysis of Sensations. Readers will also discover how in the philosophy of science he served as a model for the Vienna Circle with the Ernst Mach Society as well as paved the way for an integrated history and theory of science. Indeed, his influence extends far beyond the natural sciences -- to the Vienna Medical School and psychoanalysis (R. Bárány, J. Breuer, S. Freud), to literature (Jung Wien, R. Musil), to politics (F. Adler, Austro-Marxism and the Viennese adult education), to arts between Futurism and Minimal Art as well as to social sciences between the liberal school (J. Schumpeter, F. A. von Hayek) and empirical social research (P. Lazarsfeld und M. Jahoda).