hallucination

hallucination may be simply defined as the perception of an external object in the absence of a corresponding stimulus, yet such a simple definition obscures a whole series of conceptual difficulties which surround the medical and psychiatric use of the term. The range of conditions subsumed under this category is massive, and includes such varied phenomena as religious visions, phantom limbs, tinnitus, psychedelic ‘trips’, schizophrenic inner voices, the personal experience of doppelgangers, and a sceptical apprehension of the unreality of the outer world.

Such variety has naturally frustrated any attempt at providing a clear classification of the phenomenon. Attempts to distinguish the various forms of hallucination according to their origins, their content, their intensity, and the condition of their hosts have been largely unsuccessful. Most psychiatrists in Europe and North America have now adopted a fairly broad definition of the phenomenon, simply relying upon the distinction between illusion, which resulted from the misinterpretation of an existing external object, and hallucination, in which the false perception is generated without any reference to the outside world. Even this definition, which was introduced by the French psychiatrist J. E. D. Esquirol in the early nineteenth century, fails to account for such borderline phenomena as synaesthesia in which the sensations provoked by an object become confused, so that the subject may taste colours or see sounds.

Alongside this ongoing contest over the definition and classification of hallucination there exists a more fundamental struggle over the meaning and significance of the phenomenon. Artists and mystics have long criticized the modern medicalization of hallucinations, portraying the process as a secularizing attempt to pathologize religious or spiritual experience. Certainly popular attitudes to hallucination have been transformed across the last thousand years. In the Platonic tradition of classical philosophy, the subjective vision was celebrated as a form of privileged insight beyond the phenomenal experience of the external world. Likewise in the Christian and Jewish religions the objective quality of the inner hallucination had long been regarded as a proof of its spiritual reality, although its origin could have been either demonic or divine.

These Platonic and Christian traditions were united in the work of the Primitive Church fathers. Their writing held up the visionary experience as a charism, a gift from God which allowed individuals to perceive some object which was normally invisible to men. This conception was further refined by St Augustine, who divided visions into three classes: the corporeal, in which an apparition of an object was presented before the individual's eyes through either natural or spiritual means; the imaginative, in which an image was supernaturally created in the host's mind; and the intellectual, in which sense of personal assurance was created directly by God, without recourse to implanted words or images.

This framework for interpreting the hallucinatory experience persisted into the nineteenth century. Many romantic writers, such as Coleridge and Wordsworth, complained that normal vision enslaved the mind to the mundane world of material object. In contrast, they proposed a ‘Spiritual Optics’ (to borrow Thomas Carlyle's phrase) in which the inner eye would be awakened to the creative inspiration of the spirit. Such a programme sat unhappily with contemporary medical investigations in this field. In the late eighteenth and early nineteenth centuries, many writers commented upon the correlation between hallucination, injury, and disease. This correlation suggested that the hallucination had a somatic basis, originating in either the disordered operations of the peripheral nerves or an aberrant psychological process in the brain.

This interpretation of hallucination as a symptom of organic nervous disorder persisted throughout the nineteenth century. In 1881 the Italian psychiatrist, August Tamburini, presented a coherent neurological model for the experience, arguing that hallucination was produced through a pathological excitement or epilepsy in the higher sensory centres of the brain. This materialist account did little to diminish the mystical celebration of hallucination. Writers influenced by spiritualism and the Swedish mystic Emanuel Swedenborg accepted the scientific identification of hallucination with organic disturbance, arguing that this identity provided strong evidence for the objective reality of visions.

The mystical assessment of the significance of hallucinations was undermined by a series of psychological surveys at the end of the nineteenth century. During the 1880s the statistician, Francis Galton, circulated questionnaires on mental imagery to schools and acquaintances. From the responses he was able to demonstrate a gradation between hallucination and the familiar acts of visualization which occurred in everyday life. Galton suggested that hallucination was not a distinct experience, but rather that it represented an extreme point on two axes representing the strength of the mental image and its resistance to conscious control. This statistical erosion of the boundary between normal visualization and pathological hallucination was reinforced in a more wide-scale survey published by the Society for Psychical Research (SPR) in 1892. The SPR's ‘Census of Hallucinations’ discovered 1684 cases of waking hallucination amongst 17 000 respondents. Further analysis suggested that hallucination was most prevalent amongst women, children, and the insane, although the experience could occur in almost any individual.

In the twentieth century the hallucinatory experience seems to have lost its spiritual significance. The popular use of hallucinogenic drugs, such as LSD and psilocybin, and increased understanding of the chemical mechanisms of their actions, has encouraged a more instrumental attitude towards the visionary experience. Hallucination is no longer seen as a gratuitous event except in pathological cases such as fever or schizophrenia. Rather it is a state which can be induced directly through chemical, electrical, or mechanical means. As the neurosurgeon Wilder Penfield demonstrated, intense mental images may be created through the electrical stimulation of a subject's brain. Likewise hallucinations of movement (see proprioception) can be induced at a particular joint through the mechanical vibration of the muscles attached to it. Through such technical advances the meaning and cultural significance of hallucination has been transformed. The vision, which once revealed the mind of God to men, is now seen as a symptom revealing the disordered mind of man to others.

Rhodri Hayward

Bibliography

Berrios, G. E. (1995). The history of mental symptoms. Cambridge University Press, Cambridge.
Critchley, M. (1987). Hallucinations and their impact upon art. Carnegie Press, Preston.

See also illusions.