600. Summary of preceding chapters. While various kinds of manifestations of the Subliminal Self are disintegrative or morbid in character, we find in each class indications of higher faculties and of an evolutive potency. The converging lines of evidence lead to the conception of the Subliminal Self as the principal, deepest, and most permanent element of the Self; although much that is incoherent or outworn is also subliminal.

601. The distinctive subliminal faculty of Telepathy or Telaesthesia is emancipated from the ordinary limitations of organic life, and also persists after organic death; thus showing a relation between the subliminal and the surviving self. All subliminal action may be called Automatism and regarded under the form of messages conveying information from the subliminal to the supraliminal self, in either a sensory or a motor form.

602. Supraliminal life is here regarded as a special or privileged case of the whole personality, and consequently each ordinary faculty or sense will appear as a special case of some more general power, towards which its evolution may be tending. Each sense is generally supposed to obtain fresh information only through its own end-organ, but it will appear that new and true perceptions are also generated in the brain.

603. Vestiges of the primitive undifferentiated sensitivity persist in the form of synoesthesioe, e.g. when the hearing of an external sound carries with it, by some arbitrary association of ideas, the seeing of some form or colour. These phenomena are apparently entencephalic. 603 A. Flournoy's case. 603 B. Gruber's case.

604. The successive stages leading from these entencephalic percepts towards ordinary vision are: Entoptic impressions due to mechanical stimuli of the optic nerve or eye.

605. After-images: the retinal sequelæ of ordinary vision.

606. Ordinary external vision.

607. The further stages from entencephalic vision towards the more internal forms are: Memory-images; either cerebral sequelae of external vision, or a psychical rearrangement of these. 607 A. Flournoy on memory-images.

608. Dreams, mostly consisting of confused memory-images.

609. Imagination-images, psychical rearrangements of visual imagery.

610. All these forms of internal vision lead up to the most completely developed form, viz., hallucinations. 610 A. Mrs. Verrall on visualisation.

611. A hallucination is an intensified internal vision, a case of central hyperæsthesia. The faculty of internal vision varies in different persons, and only rarely attains to hallucination. Hallucinations sometimes arise from well-known morbid causes, but those which occur in normal conditions are more instructive, being apparently spontaneous modifications of central percepts.

612. The popular assumption that a hallucination was proof of some morbid condition was shown to be without foundation by Gurney's statistics of hallucinations occurring to persons "in good health, free from anxiety, and completely awake." Through the investigation initiated by Gurney and resumed later by a Committee of the S.P-R., a far larger collection, and one more completely representative of all classes of hallucinations than had ever existed before, was formed. It showed that for the majority of hallucinations, as for the great majority of dreams, no special explanation (either physiological or supernormal) can be offered. In most of the coincident cases, the events coinciding with the hallucinations were unknown to the percipients at the time. 612 A. Summary of the Report on the " Census of Hallucinations".

613. These veridical hallucinations afford evidence of a development of fresh faculty. The usual conformity of visual hallucinations to optical laws is the result of self-suggestion; this is true of veridical as of falsidical hallucinations.

614. But in that case, is the apparent spatial relation between percipient and percept due only to self-suggestion? Or is it not possible that real spatial relations may still exist in percepts - whether of embodied or of disembodied percipients - which have nothing to do with the sense-organs ?

615. If so, veridical mental visions may symbolically represent material objects from a point of view outside the bodily organism of the percipient, and in the place to which he imagines himself to have travelled. This excursive theory may be applied to many telepathic and to all telæsthetic cases. A corollary to it would be the possible perception of the percipient, in the place where he imagines himself to be, by other persons actually present there.

616. Mental visions can be controlled; e.g. the most effective means of checking morbid and harmful hallucinations is the influence of hypnotic suggestion on the submerged mental strata.

617. Another instance of control is the production of harmless hallucinations by hypnotic suggestion. This differs from ordinary suggestion, in which only the ordinary powers of the subject are brought into play, since it involves at least a great increase in his ordinary visualising power, and forms another example of hypnotic evocations of fresh faculty, such as were given in Chapter V (Hypnotism). The present cases are stimulations of central sensory tracts. The subliminal formation of these complex centrally initiated images is fostered by the suggestion which also projects them into the ordinary consciousness.

618. Hallucinations, then, have no necessary connection with disease, though they may often accompany it, since the central sensory tracts are of course capable of morbid as well as of healthful stimulus. The therapeutic study of hallucinations naturally preceded their psychological study; but in the newer practical study of eugenics - the study which aims at improving the human organism, instead of merely conserving it - experimental psychology is indispensable, and one branch of this is the experimental study of mental visions.