MEDIUM. - Indicates the person capable, by virtue of particular faculties, of acting as an intermediary between ourselves and the dead. However, since the spiritist hypothesis is either grave or, perhaps in some cases, merely probable (v. METAPSYCHICS; SPIRITISM), logically such a term should be abandoned; yet not only has it remained in use, but, whether or not one accepts the spiritist interpretation, it is generally employed to designate those subjects who, by reason of their particular characteristics, are considered indispensable agents in the production of metapsychic phenomena.
Much has been debated concerning the alleged necessity of mediums in metapsychic experiments; some deny it, deeming it absurd to speak of them when not even the nature of mediumship is known, and indeed when it is uncertain whether it exists at all. One fact, however, is certain: metapsychic phenomena occur only in the presence of a human being; indeed, the most extraordinary phenomena normally occur only through the participation of certain persons classified among the great mediums. If, therefore, in at least some cases, man is a necessary agent, we must conclude that there exist special faculties capable of producing such phenomena, if not adequately, then at least indispensably; apart from the choice of the term "medium" or others.
The admission of this fact, however, has nothing to do with the nature and intrinsic action of mediumship, of which we must confess our absolute ignorance to date. The theories and working hypotheses proposed by authors have not received experimental confirmation, but remain merely probable and limited to certain cases. Thus, for example, it has been suggested that mediumistic phenomena are caused by a particular energy and matter (ectoplasm) emitted by the medium in the so-called "trance" state; but, apart from the hypothetical and therefore unknown nature of such a substance, it remains utterly obscure how this occurs, that is, why the medium is capable of such operations and how they are actually performed. Hence everything appears as a complex of mysteries leaning upon other mysteries. Attempts to penetrate the inner mechanism of mediumistic action are still ongoing. At least efforts have been made to identify some of the extrinsic elements of the medium's personality; yet even here without success, for in contrast to the evident signs of suggestibility and psycho-neurosis found in many subjects, others appear entirely unaffected (v. G. C. Barnard, Il supernormale, Rome 1949, p. 113 ff). Nor is the "trance," a particular state of psychic "absence" and partial "autonomy" from the surrounding environment, often accompanied by neurovegetative manifestations (flushing, pallor, sweating, etc.), in which the medium is said to find himself during experiments, common to all subjects and seems not to be assimilable to the phenomena of imposture (v.) and the suggestive mechanism that provokes them.
In conclusion, even if mediumship is admitted as an empirical fact, it is impossible at the present time to determine the intrinsic characteristics of its action, and even less the external traits of temperament and personality in those who are its most evident and representative subjects. Nor does the practical distinction proposed by some authors between "mediums of physical effects" and "mediums of psychic effects" have any significant bearing on the intimate nature of the facts and the causes that produce them; nor do other, even more complicated systems of classification (Ch. Richet, W. Mackenzie, F. Palmés, H. Price, etc.).
From the ethical and Catholic point of view, the practice of mediumship must be judged according to the principles set forth under the heading METAPSYCHICS, to which reference is also made for a description of mediumistic phenomena. In particular, mediumship is morally forbidden when it takes place within the realm of spiritism; this is not the case, however, in general, when the phenomena concern only metapsychics as the object of scientific research. Nevertheless, mediumistic activity may and must be prohibited whenever, as often happens, it proves gravely harmful to the health—especially mental—of the person performing II.