A distinguished experimental physicist and psychophysiologist, Ernst Mach (1838–1916) was an influential worker in the foundations of physics. His main contributions in the latter were critical rather than constructive, yet important because they were concerned with certain fundamental ideas. Many of Mach's criticisms, particularly those of atomistics and Newtonian mechanics have had a profound influence. While the former was entirely negative, Mach's work on the foundations of mechanics was ambivalent.