There is a whole category of odd and fantastic doings and customs that we can group under the name of Superstitions. Some of them are merely the foolish traditions that spring up no one quite knows how or when, though antiquaries may find their traces many centuries ago, and can even at times establish relationships in traditions of this nature between the races on many continents. Some had once probably a religious significance, but they have now severed all their connection with religion, and merely enshrine evidences of what they had been formerly. But there are other practices which are far more dangerous. In themselves, indeed, there may be much that a patient and scientific study will one day succeed in establishing as of much use to humanity; but in the meanwhile they are, many of them, full of peril. For the most part they play just upon the border-line between soul and body, which we commonly call the nervous system. Hence the physical prostration they produce is often a prelude to a moral prostration, which is, of course, even more terrible. Nor should any wonder at such an effect, since the evil spirits, which our faith tells us are bent on the ruin of the human race, are clever and crafty enough to make use of every possible means of deceiving our credulity. They have ruined man time and again by the inventions of his own genius, wasting his strength and reason by means of discoveries that ease his pain or drown his sorrow.
Hence it is not surprising that they have influenced souls by the fatuous superstition of foretelling the future. Fatuous, indeed, this must ever be, since my future acts are free acts and lie at the disposition of my own soul. Even I cannot predict with certainty what I shall do. God only, because He dwells in eternity (and comprehends in His single glance the past, present, and future), can see and reveal them; the fortune-tellers do not ordinarily suggest to us the kind of people whom we can imagine God taking into His confidence. These fortune-tellers may by sheer practice come to discern character very quickly, just as a detective may be able, by the science of his trade, to determine very swiftly, by all sorts of signs that would be unnoticed by others, the temperament of those of whom he has had the opportunity of a good scrutiny. Most people are probably able by mere practice to make a pretty shrewd guess of the characters of those whom they meet; and once the temperament and characteristics of a man are known, it is not difficult to reconstruct both his past and his future. The quick-witted have their own dangers and temptations; the slow-moving and obstinate fellow can be judged to have firm friends, but few of them. And so it is possible - though obviously the game is not learnt without some difficulty - to invent details in life which come very near the truth; near enough, at any rate, to impress the most sceptical.
Indeed, so obvious does all this seem that one could hardly imagine how lucrative the trade of foretelling the future has become, nor would anyone suppose how dangerous it may be for certain souls. For some of them it has become the chief means of discovering the will of God. It is all so simple that it is difficult to see wherein the peril lies. Yet Shakespeare has shown in the marvellous structure of Macbeth how an easily moved mind can justify to itself a crime that has been foretold it, just because it has been foretold. It is evident that, had no such meeting taken place on the heath between Macbeth and the "weird sisters," the murder of Duncan would probably never have suggested itself to his mind. Till then he had been an honest, if ambitious, soldier. But the witches prophesied that he would succeed to two titles, and that eventually he would obtain the crown. He does immediately hear that he has become thane of Glamis and thane of Cawdor, and consequently his eyes now turn to the royal dignity itself. The opportunity is granted him, for Duncan comes to sleep under his very roof. Here at once he sees the gradual accomplishment of his glorious destiny. It is fate, destiny. How can he oppose himself to such heavenly evidences? His conscience at first halts and boggles at the murder of a guest; but he repeats to himself that he cannot escape, and the evil deed is done. This is, indeed, the temper of mind which itself works out the foretold future. This is the peril, that a crime, foretold and once become a possibility, may speedily (as a result of the prophecy) be an accomplished fact. It is not foretold because it will take place, but it takes place because it has been foretold.
- text taken from Meditations for Layfolk by Father Bede Jarrett, O.P.