1920. Volume 1 of a 2 volume set. A philosophical study of space, time and God. Contents Book I: Physical Space-Time; Perspectives and Sections of Physical Space-Time; Mental Space and Time; Mental Space-Time; Mathematical Space and Time; Relations in Space and Time; Book II: Nature of the Categories; Identity, Diversity and Existence; Universal, Particular and Individual; Relation; Order; Substance, Causality, Reciprocity; Quantity and Intensity; Whole and Parts, and Number; Motion, and the Categories in General; and The One and the Many. Volume 2 ISBN 0766187020.