Abstract
The father of neutral monism, Ernst Mach, argued that the fundamental constituents of the world are neither mental nor physical and that the distinction between the mental and physical ought to be erased. This article offers a reconstruction of Mach’s view. There is a “pure drive for knowledge” (reiner Erkenntnistrieb), and satisfying it, Mach argues, requires abandoning the mental/physical distinction. The reconstruction given will help to articulate and assess the differences between Mach’s position and Russell’s neutral monism, in which the distinction between the mental and physical is preserved even in the unified science of the future.