116 CRITICAL NOTICES :

subject of careful scientific study. And in order to gain any knowledge of the phenomena exceptional pains have to be taken, which may well deter most men from making the attempt. Nor is this the only difficulty. As has been observed by ancient and .modern writers, dreams are not common phenomena but confined to the individual, and this circumstance makes it extremely diffi- cult to compare observations so as to arrive at one generally acceptable theory of their nature and causes. Of late, however, the subject has been taken up with real scientific seriousness, and we may perhaps look forward to a not distant time when, as the result of a more systematic study of accessible facts, the chaos of dreamland will be reduced to psychological order. Prof. Delbceuf s volume may safely be included among the valuable works of research which have recently helped to clear up the obscurities of the subject. The volume opens with a critical sketch of some of the works on dreams those of Spitta, Eadestock, Strieker, Maudsley and others which have appeared during the last few years . While recognising in these real contributions to our knowledge of the subject, the author finds that they do not offer an adequate theory of the phenomena. Thus, to take one of the most elaborate treatises, that of Eadestock, he finds fault with its very definition of the dream, viz., the continuation of the activity of the mind during sleep, and proposes as " infinitely preferable " that given by Aristotle, "the image produced by sense-impressions when one is in a state of sleep and in so far as one sleeps". To hear faintly the barking of a dog in sleep is not, says our author, to dream. He objects to all theories that would explain dreaming by a complete suppression of certain faculties or modes of mental activity, as self-consciousness, volition, the moral sense, &c. The writer's remarks on the doubling and even the trebling of person- ality in dreams, apropos of Eadestock's theory of a suppression of self-consciousness, are peculiarly striking and suggestive. He finds in these phenomena merely a further development of the tendency of the waking mind to dramatise and give independent embodiment to the processes of thought. After this critical review Prof. Delbceuf has a first section on the relation of the dream to the theory of certitude. He begins with a distinction between perception and what he calls "conception". The former is accompanied by a belief in an external reality, which, like all belief, is the result of habit. How 7 the mind comes by such a habit of projecting sense-impressions Prof. Delbceuf does not explain beyond saying that the individual derives it from his ancestors. One is a little surprised to hear the author remark- ing that in its essential psychological characters the conception does not differ from the perception. lt The distinction between the two rests upon an extrinsic circumstance, the presence or the absence of the object as far as perceived." Eut he cannot of course help seeing that, if there is no psychological difference