As we have seen, the conceptual psychology which is the underlying paradigm for the latter nineteenth century stems from a synthesis of Empiricism and Idealism. Another name playing a role in this synthesis is Ernst Mach, an Austrian physicist, who is remembered for his delineations of the concept of "frame of reference" and the Doppler effect — that is, his work in scientific epistemology.¹ Mach's reputation is that of the psychologist among physicists. His program ranges through the culture and history of the sciences as well, including: the history of science and its relativity,² thought experiments (influencing ultimately even Einstein),³ Monism as a joint psychological and physical perspective on scientific investigation (especially in the circles around the journal The Monist),⁴ and the biological or economic adaptation of organisms — all topics at the core of Mach's psychological approach to the methodologies of science.