self-deepening, through self-realisation and self-discipline, to use to the full in our lives all that we have in heart and mind as possibilities, tendencies, content, and capacities, and so practically to experience the reality and power of the spiritual that the mood of suspicion and distrust of it must disappear. The validity of this method is corroborated by all the critical insight into the nature of our knowledge that we have gained in the course of our study, and it might be deepened in regard to this particular case. For here, if anywhere, we must recognise the limitations of our knowledge; the impossibility of attaining to a full understanding of the true nature and depths of things applies to the inquiring mind and its hidden nature. From Descartes to Leibnitz, Kant, and Fries, down to the historian of materialism itself, F. A. Lange, it has been an axiom of the idealistic philosophy, expressed now in dogmatic, now in critical form, that the mathematical-mechanical outlook and causal interpretation of things, not excluding a naturalistic psychology, is thoroughly justifiable as a method of arranging scientifically the phenomena accessible to us and of penetrating more deeply towards an understanding of these. It is, indeed, justifiable, so long as it does not profess to reveal the true nature of things, but remains conscious of the free spirit, whose own work and undertaking the whole is. Yet here again it is by no means necessary to surrender to naturalism a field which it has tried to take possession of, but is certainly unable to hold. We need not try to force naturalism to read out of empirical psychology the high conclusions as to human nature and spirit which pertain to the religious outlook, or to find in the “simplicity” of the “soul monad” a kind of physical proof of its indestructibility, or anything of that kind. We maintain that to comprehend the true inwardness of the vitality, freedom, dignity, and power of the spirit is not the business of psychology at all, but may perhaps be dealt with in ethics, if it be not admitted that with these concepts one has already entered the realm of religious experience, and that they are the very centre of religious theory. But undoubtedly we must reject in great measure the claims which naturalism makes upon our domain, and maintain that the most important starting-points for the higher view are to be found in the priority of everything spiritual over everything material, in the underivability of the spiritual and the impossibility of describing it in corporeal-mathematical terms and concepts. Individual Development.