This is a definitive edition of the works of American philosopher Charles S. Peirce, who made important contributions to symbolic logic and to the logic of science. This volume contains 66 writings from the period in Peirce’s life after he moved to Milford, Pennsylvania from New York. It includes remnants from his correspondence course in logic, by which he hoped to make a living. Other selections include: A Guess at the Riddle , Peirce’s attempt to draw his wide-ranging philosophical theories into a unified system of thought; his dispute with Edmund Gurney over Gurney’s Phantasms of the Living ; his attack under the pseudonym Outsider , on Spencer’s mechanical philosophy; and lengthy excerpts from his report on gravity which led to his forced resignation from the US Coast and Geodetic Survey.