pre-scientific conception of the dream among the ancients was certainly in perfect keeping with their general view of life, which was wont to project as reality in the outer world that which possessed reality only within the mind. It, moreover, accounted for the main impression made upon the waking life by the memory left from the dream in the morning, for in this memory the dream, as compared with the rest of the psychic content, seems something strange, coming, as it were, from another world. It would likewise be wrong to suppose that the theory of the supernatural origin of dreams lacks followers in our own day; for leaving out of consideration all bigoted and mystical authors—who are perfectly justified in adhering to the remnants of the once extensive realm of the supernatural until they have been swept away by scientific explanation—one meets even sagacious men averse to anything adventurous, who go so far as to base their religious belief in the existence and co-operation of superhuman forces on the inexplicableness of the dream manifestations (Haffner). The validity ascribed to the dream life by some schools of philosophy, e.g. the school of Schelling, is a distinct echo of the undisputed divinity of dreams in antiquity, nor is discussion closed on the subject of the mantic or prophetic power of dreams. This is due to the fact that the attempted psychological explanations are too inadequate to overcome the accumulated material, however strongly all those who devote themselves to a scientific mode of thought may feel that such assertions should be repudiated. To write a history of our scientific knowledge of dream problems is so difficult because, however valuable some parts of this knowledge may have been, no progress in definite directions has been discernible. There has been no construction of a foundation of assured results upon which future investigators could continue to build, but every new author takes up the same problems afresh and from the very beginning. Were I to follow the authors in chronological order, and give a review of the opinions each has held concerning the problems of the dream, I should be prevented from drawing a clear and complete picture of the present state of knowledge on the subject. I have therefore preferred to base the treatment upon themes rather than upon the authors, and I shall cite for each problem of the dream the material found in the literature for its solution.
But as I have not succeeded in mastering the entire literature, which is widely disseminated and interwoven with that on other subjects, I must ask my readers to rest content provided no fundamental fact or important viewpoint be lost in my description.
Until recently most authors have been led to treat the subjects of sleep and dream in the same connection, and with them they have also regularly treated analogous states of psychopathology, and other dreamlike states like hallucinations, visions, &c. In the more recent works, on the other hand, there has been a tendency to keep more closely to the theme, and to take as the subject one single question of the dream life. This change, I believe, is an expression of the conviction that enlightenment and agreement in such obscure matters can only be brought about by a series of detailed investigations. It is such a detailed investigation and one of a special psychological nature, that I would offer here. I have little occasion to study the problem of sleep, as it is essentially a psychological problem, although the change of functional determinations for the mental apparatus must be included in the character of sleep. The literature of sleep will therefore not be considered here.
A scientific interest in the phenomena of dreams as such leads to the following in part interdependent inquiries :
(a) The Relation of the Dream to the Waking State.—The naïve judgment of a person on awakening assumes that the dream—if indeed it does not originate in another world—at any rate has taken the dreamer into another world. The old physiologist, Burdach, to whom we are indebted for a careful and discriminating description of the phenomena of dreams, expressed this conviction in an often-quoted passage, p. 474: "The waking life never repeats itself with its trials and joys, its pleasures and pains, but, on the contrary, the dream aims to relieve us of these. Even when our whole mind is filled with one subject, when profound sorrow has torn our hearts or when a task has claimed the whole power of our mentality, the dream either gives us something entirely strange, or it takes for its combinations only a few elements from reality, or it only enters into the strain of our mood and symbolises reality."
L. Strümpell expresses himself to the same effect in his Nature and Origin of Dreams (p. 16), a study which is everywhere justly held in high respect: "He who dreams turns his back upon the world of waking consciousness" (p. 17). "In the dream the memory of the orderly content of the waking consciousness and its normal behaviour is as good as entirely lost" (p. 19). "The almost complete isolation of the mind in the dream from the regular normal content and course of the waking state..."
But the overwhelming majority of the authors have assumed a contrary view of the relation of the dream to waking life. Thus Haffner (p. 19): "First of all the dream is the continuation of the waking state. Our dreams always unite themselves with those ideas which have shortly before been in our consciousness. Careful examination will nearly always find a thread by which the dream has connected itself with the experience of the previous day." Weygandt (p. 6), flatly contradicts the above cited statement of Burdach: "For it may often be observed, apparently in the great majority of dreams, that they lead us directly back into everyday life, instead of releasing us from it." Maury (p. 56), says in a concise formula: "Nous rêvons de ce que nous avons vu, dit, desiré ou fait." Jessen, in his Psychology, published in 1855 (p. 530), is somewhat more explicit: "The content of dreams is more or less determined by the individual personality, by age, sex, station in life, education, habits, and by events and experiences of the whole past life."
The ancients had the same idea about the dependence of the dream content upon life. I cite Radestock (p. 139): "When Xerxes, before his march against Greece, was dissuaded from this resolution by good counsel, but was again and again incited by dreams to undertake it, one of the old rational dream-interpreters of the Persians, Artabanus, told him very appropriately that dream pictures mostly contain that of which one has been thinking while awake."
In the didactic poem of Lucretius, De Rerum Natura (IV, v. 959), occurs this passage:—
"Et quo quisque fere studio devinctus adhaeret,
aut quibus in rebus multum sumus ante morati
atque in ea ratione fuit contenta magis mens,
in somnis eadem plerumque videmur obire;
causidici causas agere et componere leges,
induperatores pugnare ac proelia obire," &c., &c.
Cicero (De Divinatione, II) says quite similarly, as does also Maury much later:—
"Maximeque reliquiae earum rerum moventur in animis et agitantur, de quibus vigilantes aut cogitavimus aut egimus."
The contradiction expressed in these two views as to the relation between dream life and waking life seems indeed insoluble. It will therefore not be out of place to mention the description of F. W. Hildebrandt (1875), who believes that the peculiarities of the dream can generally be described only by calling them a "series of contrasts which apparently shade off into contradictions" (p. 8). "The first of these contrasts is formed on the one hand by the strict isolation or seclusion of the dream from true and actual life, and on the other hand by the continuous encroachment of the one upon the other, and the constant dependency of one upon the other. The dream is something absolutely separated from the reality experienced during the waking state; one may call it an existence hermetically sealed up and separated from real life by an unsurmountable chasm. It frees us from reality, extinguishes normal recollection of reality, and places us in another world and in a totally different life, which at bottom has nothing in common with reality...." Hildebrandt then asserts that in falling asleep our whole being, with all its forms of existence, disappears "as through an invisible trap door." In the dream one is perhaps making a voyage to St. Helena in order to offer the imprisoned Napoleon something exquisite in the way of Moselle wine. One is most amicably received by the ex-emperor, and feels almost sorry when the interesting illusion is destroyed on awakening. But let us now compare the situation of the dream with reality. The dreamer has never been a wine merchant, and has no desire to become one. He has never made a sea voyage, and St. Helena is the last place he would take as destination for such a voyage. The dreamer entertains no sympathetic feeling for Napoleon, but on the contrary a strong patriotic hatred. And finally the dreamer was not yet