In accordance with the purpose as an introduction for students, the scope of the book is frankly positive and constructive. It attempts to build up an understanding of the matter of ontology in a logical manner, using simple language, illustrating the subjects with copious examples, and extracting the contents of each chapter into compact summaries. Some of the more abstruse problems of ontology, such as the problem of essence and existence, have been omitted; it was felt that the average student would derive little benefit from a lengthy discussion of problems which have taxed the ingenuity and acumen of the most profound intellects. Such problems may be attacked after the student has become acquainted with the ideas and subjects which form the foundation of the science of metaphysics. After all, the student cannot be expected to be a professional philosopher; it should be sufficient if he acquires a thorough grounding in fundamentals, so that he can deepen his knowledge through subsequent reading and study. In a general way we may define metaphysics as the science of the ultimate principles and properties of real beings.