HALLUCINATIONS.

BY EDMUND GURNEY.

SYNOPSIS OF THE ARGUMENT.

Hallucinations of the senses are first distinguished from other hallucinations, by the fact that they do not necessarily imply any false belief.

A definition of them is then given which serves to mark them off on the one hand from true perceptions, and on the other hand from remembered images or mental pictures.

The old method of distinguishing the ideational and the sensory elements in hallucinations of the senses is criticised; and it is shown that the delusive appearances are not merely imagined, but are actually seen and heard-the hallucination differing from an ordinary percept only in the fact of lacking an objective basis.

The controversy as to the physiological starting-point of the phenomena is briefly sketched; and it is shown that the creation of sensory hallucinations, which is central and the work of the brain, is quite distinct from the excitation or initiation of them, which may be peripheral and due to some other part of the body that sets the brain to work.

This excitation may even be due to some objective external cause, as is shown by the fact that the view of an imaginary object may sometimes be affected, in just the same way as the view of a real one would be, by a prism or a mirror. The imaginary object becomes (so to speak) attached to some point de repère-some visible point or mark, at or near the place where it is seen—and is thus made to follow the course of any optical illusions to which the said point or mark is subjected. But this dependence on an external stimulus does not affect the fact that the actual sensory element in the hallucination is in these, as in all other cases, created and imposed by the brain.

There are, however, a large number of hallucinations which we must suppose to be centrally initiated, as well as centrally created. Cases are considered where the hypothesis that the hallucination depends on an external stimulus, if possible, is yet very doubtful; for instance, where the imaginary object is seen in free space; or where it appears to move independently of the eye. But there are many other cases where the said hypothesis is plainly excluded; and where the excitation or initiation, if it does not take place in the brain, can only be

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due to some morbid disturbance in the sense-organs themselves. variety of instances are adduced where the assumption of such a morbid disturbance would be gratuitous or impossible; as, especially, in auditory hallucinations; in hallucinations which conform to the course of some more general delusion; in hallucinations which are voluntarily originated; and in the so-called "psychic" hallucinations, of which a new explanation is offered. A further argument for the central initiation is drawn from the fact that repose of the sense-organs seems a condition favourable to hallucinations.

This discussion as to the excitation of hallucinations is followed by a discussion as to their creation—the cerebral process which is involved in their having this or that particular (and often elaborate) form. Where in the brain does this process take place?-in the particular sensory centre concerned? or in some higher tract? Reasons are givenfor considering that both places of creation are available; that the simpler sorts of hallucination, which are often also recurrent, may take shape at the sensory centres themselves; but that the more elaborate and variable sorts must be traced to the higher origin; and that when the higher tracts are first concerned, the production of the hallucination is due to a downward escape of current to the sensory centre.

Finally, an argument for the higher origin is drawn from the special class of veridical hallucinations; the nature of which often leads us to conclude that those tracts of the percipient's brain which are the physical seat of ideas and memories were the first to be abnormally affected.

1. Definition.

Is it possible to treat hallucinations as a single class of phenomena, marked out by definite characteristics? The popular answer would no doubt be Yes-that the distinguishing characteristic is some sort of false belief. But this is an error in many of the best known cases of hallucination-that of Nicolai for instance the percipient has held, with respect to the figures that he saw or the voices that he heard, not a false but a true belief, to wit, that they did not correspond to any external reality. The only sort of hallucination which is necessarily characterised by false belief is the purely non-sensory sort -as where a person has a fixed idea that everyone is plotting against him, or that he is being secretly mesmerised from a distance. Of hallucinations of the senses, belief in their reality, though a frequent, is by no means an essential feature; a tendency to deceive is all that we can safely predicate of them.

If we seek for some further quality which shall be distinctive of both sensory and non-sensory hallucinations, the most hopeful sugges

tion would seem to be that both sorts are idiosyncratic and unshared. However false a belief may be, we do not call it a hallucination if it has been in the air," and has arisen in a natural way in a plurality of minds. This is just what an idée fixe of the kind above-mentioned never does: A may imagine that the world is plotting against him ; but B, if he spontaneously evolves a similar notion, will imagine that the world is plotting not against A, but against himself. Instances, however, are not wanting where the idée fixe of an insane person has gradually infected an associate ;* and as contact between mind and mind is, after all, the "natural way" of spreading ideas, we can make no scientific distinction between these cases and those where, e.g., the leader of a sect has instilled delusive notions into a number of (technically) sane followers. But again, hallucinations of the senses are also occasionally shared by several persons. Most of the alleged instances of this phenomenon are, no doubt, merely cases of collective illusion an agreement in the misinterpretation of sensory signs produced by a real external object; but, as the result of wide inquiries, I have encountered several instances of genuine and spontaneous collective hallucination.

If,

then, sensory and non-sensory hallucina

tions agree in being as a rule unshared, they agree also in presenting marked exceptions to the rule; which exceptions, in the sensory species, are of a peculiarly inexplicable kind. The conclusion does not seem favourable to our chance of obtaining a neat general definition which will embrace the two species; and, in abandoning the search for one, I can only point, with envy, to the convenient way in which French writers are enabled not to combine but to keep them apart, by appropriating to the non-sensory class the words délire and conception délirante.

Let us then try to fix the character of hallucinations of the senses independently. The most comprehensive view is that all our instinctive judgments of visual, auditory, and tactile phenomena are hallucinations, inasmuch as what is really nothing more than an affection of ourselves is instantly interpreted by us as an external object. In immediate perception, what we thus objectify is present sensation; in mental pictures, what we objectify is remembered or represented sensation. This is the view which has been worked out very ingeniously, and for psychological purposes very effectively, by M. Taine; but it is better adapted to a general theory of sensation than to a theory of hallucinations as such. To adopt it here

* See Dr. G. H. Savage's Note on the "Contagiousness of Delusions," in the Journal of Mental Science, January, 1881, p. 563; and the paper on “Folie à Deux," by Dr. Marandon de Montyel, in the Ann. Médico-Psych., 6th series, Vol. V., p. 28.

† De l'Intelligence, Vol. I., p. 408, &c.

would drive us to describe the diseased Nicolai-when he saw phantoms in the room, but had his mind specially directed to the fact that they were internally caused-as less hallucinated than a healthy person in the unreflective exercise of normal vision. I prefer to keep to the ordinary language which would describe Nicolai's phantoms as the real specific case of hallucination. And I should consider their distinctive characteristic to be something quite apart from the question whether or not they were actually mistaken for real figures—namely, their marked resemblance to real figures, and the consequent necessity for the exercise of memory and reflection to prevent so mistaking them. The definition of a sensory hallucination would thus be a percept which lacks, but which can only by distinct reflection be recognised as lacking, the objective basis which it suggests-where objective basis is to be taken as a short way of naming the possibility of being shared by all persons with normal senses. * It may be objected that this definition would include illusions. The objection could be obviated at the cost of a little clumsiness; but it seems sufficient to observe that illusions are merely the sprinkling of fragments of genuine hallucination on a background of true perception. And the definition seems otherwise satisfactory. For while it clearly separates hallucinations from true perceptions, it equally clearly separates them from the phenomena with which they have been perpetually identified the remembered images or mental pictures which are not perceptions at all. It serves, for instance, to distinguish,on the lines of common sense and common language, between the images of "day-dreams" and those of night-dreams. In both cases vivid images arise, to which no objective reality corresponds; and

* I have indeed referred above to collective hallucinations; but they may fairly be excluded here, not merely because they are very exceptional, but because it is a nice question for Idealism to determine how far, or in what sense, they lack an objective basis. To put an extreme case: suppose all the seeing world, save one individual, had a visual percept, the object of which nevertheless eluded all physical tests. Would the solitary individual be justified in saying that all the others were victims of a subjective delusion? And it he said so would they agree with him?

†M. Taine's definition and mode of treatment become unsatisfactory here. Regarding perceptions as in essence hallucinations, he naturally regards mental images since they are the shadowy representatives of former perceptions-as hallucinations of an embryonic sort. This metaphor commits him to showing how the embryo may develop into the full product-which will happen if the mental image be then and there externalised, as is often the case in delirium. The result of this transformation is inevitably a false hallucination; and a special connection is thus suggested between mental images and one particular sort of percept, namely the incorrect sort. But in ordinary experience, mental images are of course far more closely and constantly connected with correct percepts, M. Taine's true hallucinations, whose relics and representatives they are, than with false hallucinations, into which not one in a million of them is ever transformed.

in neither case is any distinct process of reflection applied to the discovery of this fact. But the self-evoked waking-vision is excluded from the class of hallucinations, as above defined, by the point that its lack of objective basis can be and is recognised without any such process of reflection. We have not, like Nicolai, to consider and remember, before we can decide that the friends whose faces we picture are not really in the room. We feel that our mind is active and not merely receptivethat it is the mind's eye and not the bodily sense which is at work; without attending to this fact, we have it as part of our whole conscious state. Dreams on the other hand are, as a rule, pure cases of hallucination, forcing themselves on us whether we will or no, and with an impression of objective reality which is uncontradicted by any knowledge, reflective or instinctive, that they are the creatures of our brain.

But, though our definition may be sufficient for mere purposes of classification, it takes us but a very little way towards understanding the real nature of the phenomena. It says nothing of their origin and, though it distinguishes them from mere normal acts of imagination or memory, it leaves quite undetermined the faculty or faculties actually concerned in them. And when we pass on to these further points, we find ourselves in a most perplexed field, where doctors seem to be as much at variance as philosophers. The debate, most ardently carried on in France, has produced a multitude of views; but not one of the rival theorists seems ever to have convinced any of the others. Still progress has been made, to this extent at any rate, that it is now comparatively easy to see where the disputed points lie, and to attack them with precision.

2. The Dual Nature of Hallucinations.

It was, of course, evident from the first that there was a certain duality of nature in hallucinations. In popular language, the mind and the sense were both plainly involved: the hallucinated person not only imagined such and such a thing, but imagined that he saw such and such a thing. But in the early days of the controversy, the attempts at analysing the ideational and the sensory elements were of a very crude sort. The state of hallucination used to be treated as one in which ideas and memories-while remaining ideas and memories and not sensations-owing to exceptional vividness took on the character of sensations. It was not clearly realised or remembered that sensations have no existence except as mental facts; and that, so far as a mental fact takes on the character of a sensation, it is a sensation. This was clearly stated, as a matter of personal experience, by Burdach and Müller; in the French discussions, the merit of bringing out the