Critics discussing Mark Twain's early skepticism have, to date, confined their explorations to short studies (articles or book chapters), brief references in passing, or buried their insights in discussions on other topics. Other critics ignore Twain's atheistic statements and see his beliefs as theistic or deterministic. Others ascribe his attitudes in the "dark writings" to late life disappointments. This study demonstrates that Twain's later attitudes towards religion, determinism, social reform and institutions were products of his family heritage, his social environment, and his early reading. Chapter 1 introduces the major premises of the study, and Chapter 2 reviews the critical background. Chapter 3 discusses the family and hometown influences: on Twain's skeptical thought, and Chapter A discusses Twain's early literary and philosophical influences. Chapter 5 examines Twain's early writings in letters and frontier tales and sketches, showing the development of his anti-religious attitudes. Chapter 6 concludes the study.