This book introduces the empirical tradition in American liberal religious thought, from 1860 to 1960, by exploring the thought of significant individual contributors. The first section focuses on four participants in the Free Religious Association of 1867, which supported free religion, the scientific method, and evolution: F. E. Abbot, W. J. Potter, D. A. Wasson, and M. J. Savage. The second section focuses on the empirical tradition as expressed by eight scholars from the eight scholars from the Chicago School in American liberal religious thought: S. Mathews, G. B. Foster, E. S. Ames, G. B. Smith, S. J. Case, A. E. Haydon, H. N. Wieman, and B. E. Meland.