Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. In 1903 a volume was published by the University of Chicago Press, entitled Studies in Logical Theory, as a part of the Decennial Publications of the University. The volume contained contributions by Drs. Thompson (now Mrs. Woolley), Mc Lennan, Ashley, Gore, Heidel, Stuart, and Moore, in addition to four essays by the present writer who was also general editor of the volume. The edition of the Studies being recently exhausted, the Director of the Press suggested that my own essays be reprinted, together with other studies of mine in the same field. The various contributors to the original volume cordially gave assent, and the present volume is the outcome. Chaps. ii – v, inclusive, represent (with editorial revisions, mostly omissions) the essays taken from the old volume. The first and introductory chapter has been especially written for the volume. The other essays are in part reprinted and in part rewritten, with additions, from various contributions to philosophical periodicals.