# The wonders of optics/The influence of the imagination

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THE INFLUENCE OF THE IMAGINATION.
The above facts show plainly that optical illusions find their source in the very mechanism of the organs of sight, and that without going farther than the eye itself we may discover numberless examples of these phenomena. We shall presently bring before our readers the innumerable means devised by art for deceiving the sense of sight and impressing us with sensations that are purely imaginary. But before describing these numerous pieces of apparatus we must still remain for a short time within the domain of man's faculties, and describe some of the illusions that we are subjected to by those powers of the imagination that are supposed to hold in check the five senses of the body. Our imagination, however, plays us as many tricks as our eyes, and, like them, is alternately false and true. Touch, taste, smell, hearing, and sight, are all supposed to be under its powerful influence for good or evil; but they are all deceived by it in turn, more especially the sense of sight, which we generally boast of as being the most trustworthy of them all. Were we to describe all the labyrinths into which our imagination is continually leading us, we might easily extend this little volume to one of treble the size. But our purpose is not so much to write a history of all the hallucinations to which the imagination is subject, but to cull from those already ​existing the most interesting instances in which this great faculty is alternately the victim and the tyrant of the sense of sight.
Amongst many works on this subject we may cite that of Brière de Boismont on "Hallucinations, Apparitions, Visions, &c.," from which we shall draw largely in the following pages. The examples we shall give will be those only in which the victims of the hallucination were in the full enjoyment of their mental faculties, and could healthily analyze the sensations and impressions to which they were subjected.
One of the first of these bears upon those diseases of the eye to which allusion was made in Chapter IV. Towards the end of 1833, a poor washerwoman who was tormented grievously with rheumatic pains gave up her business, and took to sewing for her livelihood. Being but little accustomed to this kind of work, she was compelled to sit over her needle late at night in order to save herself from starving. The unwonted strain upon the eyes soon brought on ophthalmia, which speedily became chronic. Nevertheless, she continued her work, and fell a prey to diplopia, or double sight in each eye. Instead of a single needle and thread, she saw four continually at work, everything else about her being similarly multiplied. At first she took no notice of the singular illusion, but at last both imagination and sight joined arms against the judgment, and the poor creature imagined that Providence had taken pity on her forlorn condition, and had worked a miracle in her favour by bestowing on her four pair of hands in order that she might do four times her usual amount of work.
The following is another instance of the passage of illusion into hallucination. A man fifty-two years old, of a plethoric constitution, after having suffered from a defect in his visual functions that caused him to see ob-​jects sometimes double, and at others upside down, suddenly showed signs of cerebral congestion, and threatened apoplexy. By proper treatment, however, he was saved for a time from the latter catastrophe, but he became permanently afflicted with strabismus, or squinting, and he suffered from a singular hallucination. His eyelids would contract, and his eyeballs would roll from side to side at more or less distant intervals. On these occasions he imagined he saw the figures of different persons that he knew moving about, and would even follow them outside his door into the other rooms of the house. He was perfectly aware that these appearances were merely the effect of the imagination, but this did not in any way detract from their appearance of reality. The man afterwards died from an attack of apoplexy.
The following examples are also cases of singular optical deception, some of them being so extraordinary as to trench upon the supernatural, and in the days of ignorance would have given those who were their victims the character of unearthly personages.
A certain English painter, who in some sort inherited the palette of Sir Joshua Reynolds, and believed himself superior in many respects to the great master, used to boast that in one year he painted over three hundred portraits, large and small. This fact seemed to Wigan a physical impossibility, and he questioned him closely as to the secret of his astonishing rapidity of execution, for he never required more than one sitting from his patrons. Wigan states that he saw him paint a miniature of a well-known personage in eight hours, which was incomparable in its fidelity to nature and finished execution. Wigan asked him to give him some details of the method he adopted, and he gave him the following answer: "When a sitter presents himself, I look at him attentively for half an hour, sketching the outlines of his features on my canvass during the ​time. I have no occasion for a longer sitting, and I pass on to some one else. When I wish to continue the first portrait, I take the sitter in my imagination, and I seat him in the chair, where I see him as distinctly as if he were really there, and I can even heighten a tint, or soften down a clumsy form at will, without altering the likeness. I look from time to time at the imaginary figure, and I go on painting. I stop now and then to examine his position, absolutely as if the original were before me; for every time I look towards the chair I see the sitter. This method of proceeding has rendered me very popular; and as I have always succeeded in catching the likeness of my patrons, they have been simply enchanted at my sparing them the tedious sittings exacted by other painters. Little by little I have begun to lose the distinction between the real and imaginary sitter, and I have often maintained stoutly that my patrons had already sat to me on the previous day. At last I became convinced that it was the real sitters that I saw, and thenceforth all became confusion. I suppose my friends took alarm at my hallucinations, for I remember nothing of what happened during the thirty years that I remained in the madhouse. This long period has left no trace on my memory, except indeed the last six months of my confinement. It seems to me, however, that when my friends talk of having visited me I have some vague recollection of the fact; but it is a subject that I do not care to pursue."
The most remarkable feature of the case is, that this artist after a lapse of thirty years resumed his pencil, and painted almost as well as when he was forced by madness to abandon his art.
This faculty of being able to evoke shadows, with which to people one's solitude, may be carried so far as to transform real persons into phantoms. Hyacinth ​Langlois, a distinguished artist, living at Rouen, tells us that Talma, with whom he was extremely intimate, confided to him that, whenever he went upon the stage, he had the power, by mere force of will, to cause the clothes and flesh of his numerous auditory to disappear, and become transformed from living beings into so many skeletons. When his imagination had peopled the house with these singular phantoms, the emotion he felt was so great that it gave his dramatic powers still greater force, and enabled him to produce the wonderful effects that have made his name so famous.
Wigan says, that he once knew a most intelligent and amiable man, who could at will evoke his own image. He often laughed at seeing his second self standing before him, the phantom appearing to laugh as heartily as himself. This illusion was for a long time a matter of amusement to him, but at last he became persuaded that he was haunted by his own double. His second self appeared to hold arguments with him continually, and beat him frequently on various points of dispute, a matter which mortified him excessively, as he was rather proud of his powers of reasoning. This gentleman, although always considered as being somewhat eccentric, was never put under the slightest restraint, and at last the creature of his imagination so tormented him, that he resolved not to live through another year. He consequently paid all his debts, arranged his affairs, and waited pistol in hand until the clock struck twelve on the 31st of December, and then deliberately blew out his brains.
In Abercromby on the Mind we read an account of the observations made by a gentleman who was the victim of illusions during the whole of a pretty long life. If he met a friend in the street, he was unable to tell at first whether he saw a real human being or only a phantom. By close examination he could detect a dif-​ference between the real person and the creature of his imagination, the features of the former being sharper and more defined than those of the phantom; but in general he was obliged to test the reality of the figure he saw by the senses of touch and hearing. He was able, by concentrating his thoughts upon the appearance of any friend, to call up his image; a power which extended even to scenes that he had witnessed. Although he could produce these hallucinations at will, he was powerless in making them disappear; and when once he succeeded in calling forth these creatures of his imagination, he never could tell how long the delusion would last. This gentleman was in the prime of life, a good man of business, and otherwise in a perfect state of mental and bodily health. A member of his family possessed the same faculty, but in a minor degree.
In 1806, General Rapp, when returning from the siege of Dantzic, having occasion to speak to the Emperor Napoleon, walked into his private room without being announced, and found him in such a profound state of abstraction, that he remained for some time unperceived by his imperial master. The General, seeing him thus perfectly motionless, fancied he must be ill, and purposely made a slight noise. Napoleon instantly turned his head, seized the General by the arm, and pointing upwards, exclaimed, "Do you see it up there?" The General, hardly knowing what to say, remained silent; but the Emperor repeated his question, and he was obliged to reply, that he saw nothing. "What," said the Emperor, "you don't see anything? You don't see my star shining before your eyes?" And becoming more and more animated, he went on to say, that the mysterious visitor had never abandoned him, that he saw it throughout all his great battles, that it always led him onward, and that he was never happy but when he was gazing at it.
​That such hallucinations have no real existence as far as the eye goes, is proved by the fact of many people who have lost their sight, being subject to them. It is hardly to be wondered at that those who by accident have been deprived of their sight, should wish so ardently to see once more the persons and sights they have taken pleasure in, that they should at last create for themselves illusions of this character. The same thing has frequently occurred with those whose sight is more or less weak. An old man of eighty, who was purblind, never sat down to a table during the last years of his life, without seeing around him a number of his friends who had long been dead, dressed in the costume of fifty years before. This old man had but one eye, which was extremely weak, and wore a pair of green preservers, in the glass of which he continually saw his own face reflected.
Doctor Dewar, of Stirling, mentioned to Abercromby a very remarkable instance of this species of hallucination. The patient, who was quite blind, never walked in the street without seeing a little old woman hobbling on before him and leaning on a stick. This apparition always disappeared when he entered his house.
Similar illusions frequently happen to every one, even the most healthy amongst us, but a little consideration soon puts them to flight. It would be useless to mention the numberless cases in which a square tower has appeared round, or where the landscape has suddenly seemed to recede from the sight. Such illusions as these have been long well known, and appreciated at their proper value; but there are others whose true cause has remained a mystery, until explained by the progress of science, such as the Spectre of the Brocken, the Fata Morgana, and the mirage.
Analogous appearances have been seen in Westmoreland and other mountainous districts, the inhabitants ​imagining that the air was full of troops of cavalry, and whole armies even; such illusions resulting simply from the shadows of men and horses passing over an opposite mountain being thrown on the fog.
A vast number of different circumstances give rise to these illusions, such as a strong impression, or the recollection of some striking event, which may easily cause them, by the association of ideas. Wigan relates, that being at a soirée held at the house of M. Bellart, a few days after the execution of Marshal Ney, the groom of the chamber, instead of calling out the name of M. Maréchal aîné (M. Maréchal, senior), announced the arrival of M. le Maréchal Ney. A shudder passed through the company, and many of them declared, that for an instant they saw the face and figure of the dead man in place of those of his involuntary representative.
When the mind is thus prepared, the most familiar objects are transformed into phantoms. Ellis relates an anecdote of this kind, which he heard from an eye-witness, who was a ship's captain of Newcastle-on-Tyne. During a voyage that he made, the ship's cook died. Some days after the funeral, the chief mate came running to him in a great fright, with the news that the ship's cook was walking on the water, astern of the vessel, and that all the crew were on deck looking at him. The captain, who was angry at being disturbed with so nonsensical a tale, answered sharply, that they had better put the ship about and race the ghost to Newcastle. His curiosity, however, was presently aroused, and he went upon deck and looked at the spectre. He frankly avowed that for some moments he saw what really appeared to be his old shipmate, just as he knew him in life, with his walk, clothes, cap and figure perfectly resembling those of the dead man. The panic became general, and every one was struck motionless for a time. He had the presence of mind, however, to ​seize the helm and put the ship about, when as they neared the ghost, they found the absurd cause of their fright was a broken mast from some wreck, which was floating after them in an upright position. If the captain had not boldly sailed up to the supposed ghost, the story of the dead cook walking upon the water would have continued to this day to terrify half the good inhabitants of Newcastle.
Such facts as these are innumerable, and we shall mention a few more which will explain a host of stories found in various ancient and modern authors.
Ajax was so angry at the arms of Achilles being awarded to Ulysses, that he became furious, and, seeing a herd of pigs, drew his sword and fell upon them, taking them for Greeks. He next seized a couple of them and beat them cruelly, loading them at the same time with insults, imagining one of them to be Agamemnon, his judge, and the other Ulysses, his enemy. When he came to himself, he was so ashamed at what he had done, that he stabbed himself with his sword.
Theodoric, blinded by jealousy and yielding to the base solicitations of his courtiers, ordered that Symmachus, one of the most upright men of his time, should be put to death. The cruel order had hardly been executed, when the king was seized with remorse, and bitterly reproached himself with his crime. One day a new kind of fish was put upon the table, when the king suddenly cried out that he saw in the head of the fish the absolute resemblance of that of his victim. This vision had the effect of plunging the king into a state of melancholy that lasted his whole life.
Bessus once, when surrounded by his guests and giving himself up to the enjoyment of the feast, ceased suddenly to listen to the flattering speeches of his courtiers. He apparently listened with great attention to some sound that was heard by no one else, and suddenly ​leaping from his couch, mad with rage, he seized his sword and rushing at a swallow's nest that was near, beat it down, killing the poor birds inside it, crying out that these insolent birds dared to reproach him with the murder of his father. Surprised at such a sight, his courtiers gradually disappeared, and it became known some time afterwards that Bessus was really guilty, and that the senseless action he had performed simply resulted from the voice of conscience.
The illusions of sight and hearing are often found to take an epidemic form, and historians relate an immense number of anecdotes bearing on this particular phase of self-delusion. One of the commonest of them is that which transforms the clouds into armies and figures of all kinds. Religious prejudices, optical phenomena, physical laws that are still unknown, dangerous fevers, derangements of the brain, afford a natural explanation of these hallucinations.
We have borrowed most of these examples from Brière de Boismont's works, for the special purpose of showing how easy it is to deceive the imagination, and to demonstrate the facility with which the sense of sight is led astray without the intervention of complicated apparatus. In addition, we may quote instances from Brewster, showing the ease with which the imagination enables us to see distinct forms in a confused mass of flames, or in a number of shadows superposed upon each other. This great philosopher gives us an anecdote of Peter Heamann, a Swedish pirate and murderer. One day that his crew were repairing some unimportant portion of the ship, after having pitched the place well he took the brush in order to tar the other parts of the vessel, which were much in want of such treatment; but as soon as he spread the pitch over the timbers of the ship, he was thunderstruck at seeing apparently reflected in its shining surface the image of a gallows ​with a headless man beneath. The head belonging to the body was lying before it, and the body itself was depicted with every limb—legs, thighs, and arms—perfect. He frequently told his crew of these illusions, adding that it was evidently a prediction of the fate in store for them. He was often in such a state of terror, that on calm days he would drop down into the hold and wrap himself up in a spare sail in order not to catch sight of the horrible image that he constantly saw in the shining surface of the tar.
The imagination really seems to create for itself a sort of mental visual organ which is in intimate relation with that of the body, and which often takes its place so efficiently—as in the case of dreams—that the mind is utterly unable to perceive the substitution. It is on account of this that practical opticians are so unsparing in their endeavours to predispose their spectators to being deceived.
When both the body and mind are healthy, the relative intensity of the two kinds of impressions is very unequally divided, mental images being more evanescent and comparatively weak, and with persons of ordinary temperament incapable of effacing or disturbing the reflections of visible objects. The affairs of life could not go on if the memory introduced amongst them brilliant representations of the past in the midst of ordinary domestic scenes or the objects familiar to us. We may account for this by supposing that the set of nerves which carries the efforts of the memory to the brain cannot execute their functions at the same time as those which take cognizance of the images reflected on the retina. In other words, the mind cannot accomplish two separate functions at one and the same time, and the mere act of directing the attention to one class of subjects causes all others to become instantly imperceptible. The exercise of the mind in these instances is, ​however, so rapid that the alternate appearance and disappearance of the two different impressions is completely unnoticed. Thus, for instance, while looking at the dome of St. Paul's, if our memory suddenly evokes the image of some other object, Mont Blanc for instance, the picture of the cathedral, although still depicted on our retina, is momentarily effaced by the effort of the will, although we may not change the position of our eyes during the time. While the memory continues to dwell on the picture it has called up, it is seen with sufficient distinctness, although its details may be somewhat misty and its colours confused; but as soon as the wish to see it passes away the whole disappears, and the cathedral is seen in all its former distinctness.
In darkness and solitude, when surrounding objects produce no images that can interfere with those of the mind, these latter are more lively and distinct: and when in addition we are half asleep and half awake, the intensity of mental impressions approaches that of visible objects. In the case of persons of studious habits who are continually employed in mental effort, these images are more distinct than with those who follow the ordinary avocations of life, and during their working hours rarely see the objects round them. The earnest thinker, absorbed by meditation, is in a manner deprived for the time of the use of his senses. His children and servants pass in and out of his study without his seeing them, they speak to him without his hearing them and they may even try to rouse him from his reverie without success; and yet his eyes, ears, and nerves received the impression of light, sound, and touch. In such instances, the mind of the philosopher is voluntarily occupied in following out an idea which interests him profoundly; but even the most unlearned and thoughtless of us sees the images of dead ​or absent friends with his mind's eye, or even fantastic figures which have nothing to do with the train of thought he may be pursuing. It is with these involuntary apparitions as with spectres of the imagination: although they are intimately connected with some thought that has passed through our mind unperceived, it is impossible to trace a single link of the chain connecting them together.