This volume presents new essays on the work and thought of physicist, psychologist, and philosopher Ernst Mach. Moving away from previous estimations of Mach as a pre-logical positivist, the essays reflect his rehabilitation as a thinker of direct relevance to debates in the contemporary philosophies of natural science, psychology, metaphysics, and mind. Topics covered include Mach's work on acoustical psychophysics and physics; his ideas on analogy and the principle of conservation of energy; the correct interpretation of his scheme of 'elements' and its relationship to his 'historical-critical' method; the relationship of his thought to movements such as American pragmatism, realism, and neutral monism, as well as to contemporary figures such as Friedrich Nietzsche; and the reception and influence of his works in Germany and Austria, particularly by the Vienna Circle.