1994 0-7734-9122-8 This study contributes to scholarship in five ways. It provides a unified framework within which to view the development of Presocratic thought; it points out three aspects of Xenophanes' skepticism, and shows that (and how) Heraclitus responded to each; it summarizes key issues concerning psyche and logos, and attempts to settle certain long-standing debates concerning them; it argues that Heraclitus' concepts of psyche and logos resulted from his need to construct an epistemological theory in order to counter Xenophanean skepticism; and it make use of various traditional Greek assumptions such as the principles of "like-to-like," the analogy of microcosm and macrocosm, and the concepts of balance and measure as exemplified in the ideal of sophrosune.