Section — Slater, Manual of Moral Theology
Section IV. Vain Observance
The term vain observance is used by theologians to designate various kinds of superstition by which altogether disproportionate means are employed to procure a sure and certain effect. It comprises the use of charms, spells, and cabalistic signs, which are used to preserve persons and things from harm, or cure wounds and diseases, or acquire knowledge without the labour of study. It also signifies the superstitious observance of chance events and days, some of which are considered lucky, others unlucky. Magic is the art of wonderworking by the help of the devil.
p. i, 144
Vain observance, or witchcraft and magic, is gravely sinful for precisely similar reasons as divination is. There is only an accidental difference between these kinds of superstition, for while divination uses disproportionate means to discover what is hidden by the help of the devil, witchcraft uses disproportionate means to obtain certain and wonderful effects by his help. Morally, therefore, there is no difference between divination and witchcraft. Like divination, witchcraft may contain an express or tacit compact with the devil, and although if the compact be express there will always be mortal sin, there will frequently be only venial when the compact is tacit. Ignorance or good faith or want of full confidence in the effect will in that case frequently excuse from serious sin. Moreover, there must be advertence to the total inadequacy of the means to obtain the effect desired, and to the danger of the devil’s intervention, otherwise there will not be the sin of superstition. And so people who do not like to undertake any journey on a Friday, or to sit down with thirteen 1 Summa Theol., 2-2, q. 96, a. 3, ad 2. at table, because they have always heard that it is unlucky, and because their fathers had similar scruples, may often be excused from sin.
p. i, 144–145
In a case of doubt whether a particular effect is to be ascribed to natural causes or not, we should rather ascribe it to natural causes than to the devil, for we must not bring in the preternatural without necessity, and we do not yet know all the forces of nature. Thus many believe that telepathy really exists and is due to natural causes. In such a case of doubt, then, we may experiment and investigate the matter; it is advisable to renounce all intention of dealing with the devil as a precautionary measure. If, on the contrary, it is certain that the effect is not attributable to natural causes, it should be ascribed to the devil rather than to God in case of doubt; for God does not work miracles without good reason, and ordinarily the sanctity of the person concerned and other circumstances clearly show divine intervention when it takes place.
p. i, 145
Many theologians hold that the phenomena of hypnotism are due to preternatural causes, and consequently they maintain that it is unlawful to induce the hypnotic state or to have any part in it. Others more probably think that the state itself and the susceptibility of the hypnotized subject to suggestion on the part of the hypnotizer, together with those phenomena which affect the bodily organs and the imagination, are due to natural causes. The rarer phenomena of clairvoyance by which scenes and passing events at a great distance are seen, or by which an ignorant medium shows knowledge which is not possessed in the normal state, must be attributed to preternatural causes. For it seems impossible that natural forces should be able to produce effects altogether beyond their range. Even if we admit that the hypnotic state and the bodily phenomena are due to natural causes, it does not follow that anyone may induce the hypnotic sleep merely for the sake of experiment or out of curiosity. Such a practice would be accompanied with grave dangers, moral and physical, and it is not lawful to permit one’s self to be deprived. of the use of reason, and to subject one’s self to another’s control, without good cause and proper safeguards. Medical men, however, and other persons of skill and experience cannot be precluded from using a means which is very probably innocent, with proper precautions and for a good reason,
p. i, 145