At the turn of the century, Charles S. Peirce (1839-1914) shared his considerable experience as a writer of dictionary and cyclopedia entries with James Mark Baldwin, who was editing his landmark Dictionary of Philosophy and Psychology (1901-1905). Peirce contributed nearly two-hundred definitions to this dictionary. Some as single author and others as a collaborator with thinkers such as Josiah Royce, William James, and G.E. Moore. This volume introduces and assembles for the first time all of these contributions including drafts of many that were not included in the published dictionary. Peirce’s entries for Baldwin’s Dictionary are one of the most extensive, important, and impactful contributions to philosophical terminology in the American canon.