in the fourth volume. ... I have introduced in an appendix to the third volume, some matter of philosophical interest for which there was no place in the editorial prefaces or in the annotations. The historical significance of Samuel Johnson and Jonathan Edwards, as pioneers of American philosophy, and also advocates of the new conception of the material world that is associated with Berkeley, is recognized in Appendix C. Illustrations of the misinterpretation of Berkeley by his early critics are presented in Appendix D. A lately discovered tractate by Berkeley [an essay entitled "Of Infinities"] forms Appendix E. In the fourth volume numerous queries contained in the first edition of the Querist, and omitted in the later editions, are given in an appendix which enables the reader to reconstruct that interesting tract in the form in which it originally appeared.
The present edition is thus really a new work, which possesses, I hope, a certain philosophical unity, as well as pervading philosophical interest."
As is stated in its preface, this book is an attempt to discover the simple mental processes that manifest themselves in the belief in the existence of the external world and of the mental life of others. Throughout the discussion there is an occasional appeal to experimental psychology, a procedure that continually suggests the question whether experimental psychology is at present in a condition to furnish even a partial basis for any satisfactory epistemological theory. Every attempt to utilize its results, however, is of double value; for apart from the soundness or unsoundness of the theory propounded, a clearer conception is gained of what is yet to be done, before psychology can be regarded as an approximately complete science, and therefore as an adequate foundation for any other discipline.
The author begins with the essential isolation of each individual, which makes it impossible for anyone to go beyond his own experience, and points out that one of the factors in this experience is the idea of something outside itself, something not experienced. This idea or belief may take either one of two forms: (1) That something remains hidden behind experiences, which continues to exist even when they cease; and (2) that one's neighbor has experiences distinct from one's own. After a strict determination of the meaning of the terms to be used, in which we need notice only the definition of experience as that which can be compared, an examination is made of the seven "psychological riddles," which are regarded as ultimate for experience, and so as incapable of explanation. They are the psychical elements, comparison, consciousness of succession, expectation, identification or substitution, the idea of external reality, and that of an experience other than one's own. The last two are assumed
