The limits between illusions of sense and hallucinations and illusions
proper can in no sense be definitely determined inasmuch as any
phenomena of the one may be applied to the other, and vice versa.[321]
Most safely it may be held that the cause of illusions of sense lies in
the nature of sense-organs, while the hallucinations and illusions are
due to the activity of the brain. The latter are much more likely to
fall within the scope of the physician than sense-illusions, but at the
same time many of them have to be determined upon by the lawyer,
inasmuch as they really occur to normal people or to such whose disease
is just beginning so that the physician can not yet reach it.
Nevertheless, whenever the lawyer finds himself face to face with a
supposed illusion or hallucination he must absolutely call in the
physician. For, as rarely as an ordinary illusion of sense is explicable
by the rules of logic or psychology, or even by means of other knowledge
or experience at the command of any educated man, so, frequently, do
processes occur in cases of hallucination and illusion which require, at
the very least, the physiological knowledge of the physician. Our
activity must hence be limited to the perception of the presence of
hallucination or illusion; the rest is matter for the psychiatrist.
Small as our concern is, it is important and difficult, for on the one
hand we must not appeal to the physician about every stupid fancy or
every lie a prisoner utters, and on the other hand we assume a heavy
responsibility if we interpret a real hallucination or illusion as a
true and real observation. To acquire knowledge of the nature of these
things, therefore, can not be rigorously enough recommended.
Hallucination and illusion have been distinguished by the fact that
hallucination implies no external object whatever, while in illusion
objects are mistaken and misinterpreted. When one thing is taken for
another, e.g., an oven for a man, the rustle of the wind for a human
song, we have illusion. When no objective existence is perceived, e.g.,
when a man is seen to enter, a voice is heard, a touch is felt, although
nothing whatever has happened, we have hallucination. Illusion is
partial, hallucination complete, supplementation of an external object.
There is not a correct and definite difference between illusion and
hallucination inasmuch as what is present may be so remotely connected
with what is perceived that it is no more than a stimulus, and thus
illusion may be turned into real hallucination. One authority calls
illusion the conception of an actually present external event which is
perceived by the peripheral organs in the form of an idea that does not
coincide with the event. The mistake does not lie in the defective
activity of the senses so much as in the fact that an apperceptive idea
is substituted for the perceptive view. In hallucination every external
event is absent, and hence, what is seen is due to a stimulation of the
periphery. Some authorities believe hallucination to be caused by cramp
of the sensory nerve. Others find illusions to be an externally
stimulated sense-perception not corresponding to the stimulus, and still
others believe it to be essentially normal. Most human beings are from
time to time subject to illusions; indeed, nobody is always sober and
intelligent in all his perceptions and convictions. The luminous center
of our intelligent perceptions is wrapped in a cloudy half-shadow of
illusion.
Sully[322] aims to distinguish the essential nature of illusion from
that characterized by ordinary language. Illusion, according to him, is
often used to denote mistakes which do not imply untrue perceptions. We
say a man has an illusion who thinks too much of himself, or when he
tells stories otherwise than as they happen because of a weakness of
memory. Illusion is every form of mistake which substitutes any direct
self-evident or intuitive knowledge, whether as sense-perception or as
any other form.
Nowadays the cause of hallucination and illusion is sought in the
over-excitement of the cerebro-spinal system. As this stimulation may be
very various in its intensity and significance, from the momentary rush
of blood to complete lunacy, so hallucinations and illusions may be
insignificant or signs of very serious mental disturbances. When we seek
the form of these phenomena, we find that all those psychical events
belong to it which have not been _purposely_ performed or lied about.
When Brutus sees Cæsar’s ghost; Macbeth, Banquo’s ghost; Nicholas, his
son; these are distinctly hallucinations or illusions of the same kind
as those “really and truly” seen by our nurses. The stories of such
people have no significance for the criminalist, but if a person has
seen an entering thief, an escaping murderer, a bloody corpse, or some
similar object of criminal law, and these are hallucinations like
classical ghosts, then are we likely to be much deceived. Hoppe[323]
enumerates hallucinations of apparently sound (?) people. 1. A priest
tired by mental exertion, saw, while he was writing, a boy’s head look
over his shoulder. If he turned toward it it disappeared, if he resumed
writing it reappeared. 2. “A thoroughly intelligent” man always was
seeing a skeleton. 3. Pascal, after a heavy blow, saw a fiery abyss into
which he was afraid he would fall. 4. A man who had seen an enormous
fire, for a long time afterward saw flames continually. 5. Numerous
cases in which criminals, especially murderers, always had their victims
before their eyes. 6. Justus Möser saw well-known flowers and
geometrical figures very distinctly. 7. Bonnet knows a “healthy” man who
saw people, birds, etc., with open eyes. 8. A man got a wound in his
left ear and for weeks afterward saw a cat. 9. A woman eighty-eight
years old often saw everything covered with flowers,--otherwise she was
quite “well.”
A part of these stories seems considerably fictitious, a part applies to
indubitable pathological cases, and certain of them are confirmed
elsewhere. That murderers, particularly women-murderers of children,
often see their victims is well known to us criminalists. And for this
reason the habit of confining prisoners in a dark cell for twenty-four
hours on the anniversary of a crime must be pointed to as refined and
thoroughly mediæval cruelty. I have repeatedly heard from people so
tortured of the terror of their visions on such days of martyrdom. Cases
are told of in which prisoners who were constipated had all kinds of
visual and auditory hallucinations and appeared, e.g., to hear in the
rustling of their straw, all sorts of words. That isolation predisposes
people to such things is as well known as the fact that constipation
causes a rush of blood to the head, and hence, nervous excitement. The
well-known stories of robbers which are often told us by prisoners are
not always the fruit of malicious invention. Probably a not
insignificant portion are the result of hallucination.
Hoppe tells of a great group of hallucinations in conditions of waking
and half-waking, and asserts that everybody has them and can note them
if he gives his attention thereto. This may be an exaggeration, but it
is true that a healthy person in any way excited or afraid may hear all
kinds of things in the crackling of a fire, etc., and may see all kinds
of things, in smoke, in clouds, etc. The movement of portraits and
statues is particularly characteristic, especially in dim light, and
under unstable emotional conditions. I own a relief by Ghiberti called
the “Rise of the Flesh,” in which seven lemurs dance around a corpse and
sing. If, at night, I put out the lamp in my study and the moon falls on
the work, the seven lemurs dance as lively as may be during the time it
takes my eyes to adapt themselves from the lamplight to the moonlight.
Something similar I see on an old carved dresser. The carving is so
delicate that in dim light it shows tiny heads and flames after the
fashion of the Catholic church pictures of “poor souls,” in purgatory.
Under certain conditions of illumination the flames flicker, the heads
move, and out of the fire the arms raise themselves to the clouds
floating above. Now this requires no unusual excitement, simply the
weary sensing of evening, when the eyes turn from prolonged uniform
reading or writing to something else.[324] It has happened to me from my
earliest childhood. High bodily temperature may easily cause
hallucinations. Thus, marching soldiers are led to shoot at nonexisting
animals and apparently-approaching enemies. Uniform and fatiguing mental
activity is also a source of hallucination. Fechner says that one day
having performed a long experiment with the help of a stop-watch, he
heard its beats through the whole evening after. So again when he was
studying long series of figures he used to see them at night in the dark
so distinctly that he could read them off.
Then there are illusions of touch which may be criminalistically
important. A movement of air may be taken for an approaching man. A
tight collar or cravat may excite the image of being stifled! Old people
frequently have a sandy taste while eating,--when this is told the
thought occurs that it may be due to coarsely powdered arsenic, yet it
may be merely illusion.
The slightest abnormality makes hallucinations and illusions very easy.
Persons who are in great danger have all kinds of hallucinations,
particularly of people. In the court of law, when witnesses who have
been assaulted testify to having seen people, hallucination may often be
the basis of their evidence. Hunger again, or loss of blood, gives rise
to the most various hallucinations. Menstruation and hæmorrhoids may be
the occasions of definite periodic visions, and great pain may be
accompanied by hallucinations which begin with the pain, become more
distinct as it increases, and disappear when it ceases.
It might seem that in this matter, also, the results are destructive and
that the statements of witnesses are untrue and unreliable. I do not
assert that our valuation of these statements shall be checked from all
possible directions, but I do say that much of what we have considered
as true depends only on illusions in the broad sense of the word and
that it is our duty before all things rigorously to test everything that
underlies our researches.