tive similarity of other men with one’s self. The I-experience and the environment-experience (Umgebungs-erfah.) mutually involve and belong to each other; that is, in a word, this co-ordination that accompanies all experience in which that which is called ‘I’ is a constant member, and that which is called ‘tree’ or ‘fellow-man’ is a varying member, is the principle of our experience; Professor Avenarius calls it die empiriokritische Principal ko-ordination. Thus the great fact of experience, the world-formula, is constancy through variation; this, though, agrees exactly with the natural world-concept—Variationserscheinungen. Introjection, then, does not lead us to a dualism or to a rejection of the world-concept that is formed by experience. The book is excessively hard reading, for the reason is unfolded in a series of paragraphs whose only connection beyond their numbering is the arbitrary, conquering march of the author’s thought, which, too, is condensed, technical, and symbolical [mathematical formulae abound in it]. The tone of it is that of a Selbstbefreiung, as is admitted in it, and it is hardly, therefore, to be treated as a didactic exposition of any kind. We have really before us a systematized phenomenology of knowledge in its transition from naïve realism in which object and perception, being and thought, are not distinguished to self-consciousness or reflected knowledge, through the discriminative work of the logical understanding and the hypothetical constructions of the imagination as seen in different stages of human culture. The thought is undoubtedly masterly but too technical and idiosyncratic to induce the ordinarily diligent reader to follow it through all its mazes and over all its hard barriers; the merit of it lies in its combination of the critical and the empirical modes of philosophizing.
We have here the first volume of what promises to be a very thorough and detailed account of the philosophy of arithmetic. The present instalment is a valuable contribution to the understanding of the fundamental concepts underlying the science 'of number. The undertaking is a significant one, if only in the sense that it marks a new departure in logic. Hitherto the modern tendency to specialization has not appeared in this department, works on logic contenting themselves with a meagre account of the philosophy of the sciences. Dr. Husserl describes the field of his research as a circle within many circles, and directs his attention to the principles of a single science.
