Ernst Mach and the Fortunes of Positivism in America

B ETWEEN 1910 AND 1914, the Nobel Committee in Stockholm received a number of letters and petitions from scientists nominating Ernst Mach for the Nobel Prize in physics (see Figure 1). Among these, H. A. Lorentz praised Mach's "beautiful works," especially in acoustics and optics, which indeed have not lost their luster to this day; but he added that "all physicists" know Mach's historical and methodological books, and "a large number of physicists honor him as a master and as a guide of their thoughts." (A few years later, in his obituary for Mach in 1916, Albert Einstein said it more strikingly: "I believe even that those who consider themselves as opponents of Mach are hardly aware of how much of Mach's way of thinking they imbibed, so to speak, with their mother's milk.") Ferdinand Braun's nominating letter indicated that while the Nobel Prize might soon have to be awarded for the new theory of space and time, it should first go to Mach, as an early advocate of ideas along the same lines as well as a major experimental physicist; but Braun, too, insisted on Mach's wider influence through philosophical clarifications and "his clear, profound historicalphysical studies."'1 As is well known, only a few years before those letters were sent to Stockholm, Einstein-who later confessed in his Autobiography that Mach's Mechanik had "exercised a profound influence" upon him, and that Mach's example of critical reasoning had been a requirement for his discovering the key to relativity-signed one of his letters to Mach "Your admiring student."2 Similarly, the next generation of physicists, which struggled with the problems of the new quantum mechanics (e.g., Werner Heisenberg and Wolfgang Pauli), also found in Mach guidance for their thoughts. At least among scientists, Mach was recognized as one of the most effective fighters in the empiricist challenge to notions implying "absolutes" that had in-