The transformation of an idea into an hallucination is not the only deviation of the dream from a waking thought which perhaps corresponds to it. From these pictures the dream forms a situation, it presents something in the present, it dramatises an idea, as Spitta[64] (p. 145) puts it.[K] But the characteristic of this side of the dream life becomes complete only when it is remembered that while dreaming we do not—as a rule; the exceptions require a special explanation—imagine that we are thinking, but that we are living through an experience, _i.e._, we accept the hallucination with full belief. The criticism that this has not been experienced but only thought in a peculiar manner—dreamt—comes to us only on awakening. This character distinguishes the genuine sleeping dream from day dreaming, which is never confused with reality. The characteristics of the dream life thus far considered have been summed up by Burdach[8] (p. 476) in the following sentences: “As characteristic features of the dream we may add (_a_) that the subjective activity of our mind appears as objective, inasmuch as our faculty of perception perceives the products of phantasy as if they were sensory activities ... (_b_) sleep abrogates one’s self-command, hence falling asleep necessitates a certain amount of passivity.... The slumber pictures are conditioned by the relaxation of one’s self-command.” It is a question now of attempting to explain the credulity of the mind in reference to the dream hallucinations, which can only appear after the suspension of a certain arbitrary activity. Strümpell[66] asserts that the mind behaves in this respect correctly, and in conformity with its mechanism. The dream elements are by no means mere presentations, but true and real experiences of the mind, similar to those that appear in the waking state as a result of the senses (p. 34). Whereas in the waking state the mind represents and thinks in word pictures and language, in the dream it represents and thinks in real tangible pictures (p. 35). Besides, the dream manifests a consciousness of space by transferring the sensations and pictures, just as in the waking state, into an outer space (p. 36). It must therefore be admitted that the mind in the dream is in the same relation to its pictures and perceptions as in the waking state (p. 43). If, however, it is thereby led astray, this is due to the fact that it lacks in sleep the criticism which alone can distinguish between the sensory perceptions emanating from within or from without. It cannot subject its pictures to the tests which alone can prove their objective reality. It furthermore neglects to differentiate between pictures that are arbitrarily interchanged and others where there is no free choice. It errs because it cannot apply to its content the law of causality (p. 58). In brief, its alienation from the outer world contains also the reason for its belief in the subjective dream world.