In writing these words Laplace hardly thought of telepathy, of the spirits, or the movements of objects without contact, but only of animal magnetism, which represented the supernormal of his time. This passage remains none the less the rule of conduct to be followed concerning all the possible manifestations of this multiform subject. Two inseparable facts, completing each other, as the faces of a medal, may be distinguished in it; but it is advisable, in order to place them the better in the light, to formulate them separately into two propositions representing the governing principles, the axioms of all investigations of the supernormal. The one, which I shall call “Principle of Hamlet,” may be condensed. in these words: All is possible. The other, to which it is but just to leave the name of “Principle Of Laplace,” is susceptible of many forms of expression. I shall express it thus: The weight of the evidence should be proportioned to the strangeness of the facts.
The forgetfulness of the “Principle of Hamlet” makes the “strong minds,” for whom the limits of nature would not exceed those of their system, the simpleton popes of all times and of all kinds, from the burlesque adversaries of Galileo to the poor Auguste Comte, declaring that the physical constitution of the stars would never be known, and to his noble rivals of the learned societies, denying the aërolites or condemning railroads beforehand. In its turn, the ignorance of the “Principle of Laplace” makes the “credulous souls,” who have never reflected that, if all is possible to the eyes of the modest seeker, all is, however, not certain, or even equally possible, and that some evidence would yet be necessary in order to suppose that a stone falling on the floor in an occult reunion arrived there through the walls by the aid of a dematerialization, rather than to admit that it came there in the pocket of a joker.
Thanks to these axioms, the investigator will avoid the doubly signalled danger, and will advance without fear into the labyrinth of the supernormal in advance of the monsters of the occult. However fantastic and magical the things may be which will spring up before his eyes or which will fill his ears, he will never be taken unawares, but, expecting all in the name of the “Principle of Hamlet,” he will not be astonished at anything, and simply say: “Be it so! Why not? We shall see.” On the other hand, he will not allow the wool to be pulled over his eyes, and he will not easily be satisfied in the matter of evidence; but, firmly intrenched behind the “Principle of Laplace,” he will show himself all the more exacting as to the proofs, in proportion to the degree in which the phenomena or the conclusion, which they may wish him to accept, may be extraordinary, and he will oppose a merciless non liquet to every demonstration which still seems suspicious or lame.
I wish to speak a word here of the inevitable rôle which the personal coefficient of the turn of mind and character plays in the concrete application of the “Principle of Laplace.” This latter is of a vagueness and a deplorable elasticity which opens the door to all divergences of individual appreciation. If we could express in a precise manner and translate in ciphers, on the one hand, the strangeness of a fact, which makes it improbable; on the other hand, the weight of evidence which tends to make it admissible; and, finally, the demandable proportion between these two contrary factors, so that the second may counterbalance the first and secure assent—that would be perfect, and everybody would soon come to an agreement. Unhappily, the means to accomplish this result is not yet perceived.
We must pass now to the weight of the evidence. We may, up to a certain point, submit it to an objective judgment and to an impartial estimation by following the rules and methods of logic, in the broadest sense of the term. But the strangeness of the facts, or, as Laplace said, the difficulty in admitting them! Who, then, is to be the judge of them, and by what universal standard can we measure them?
We must recognize that we are here in presence of an eminently subjective and emotional factor, changeable from one individual to another.
It is necessary to take some stand. In the matter of the supernormal there are too many interior and personal factors (intellectual idiosyncrasies, æsthetic temperaments, moral and religious sentiments, metaphysical tendencies, etc.) tending to determine the quality and intensity of the characteristic of the strangeness in the facts in litigation, to enable one to flatter himself upon a disinterested, objective, and quasi-scientific verdict upon their degree of probability or improbability. It is only when, after the accumulation of cases and evidences of similar character, a tacit agreement shall finally have been reached by those who have studied the subject, that the problem can be said to be solved, either by the relegation of pretended supernormal phenomena to the domain of vanished illusions and abandoned superstitions, or by the recognition of new laws and forces in nature. The phenomena considered till then as supernatural will cease to be so; they will form a part of established science, they will have nothing more in them that is strange, and will be admitted by everybody. As long as this mile-post is not reached, as long as the supernormal phenomenon is discussed as such, there are but individual opinions on this subject, subjective certitudes or probabilities, verdicts in which reality is only reflected as closely welded to the personality of their authors.
Two suggestions seem to me to spring from this. First, authors who take it upon themselves to give their advice upon the extraordinary facts coming to their knowledge ought always to begin by making their confession, so that the reader may the better distinguish the intimate factors which may have influenced them. It is true that we are not always thoroughly acquainted with ourselves, but it would be something to say frankly what we believe we have discovered in ourselves as to the position involuntarily taken by us, obscure inclinations for or against the hypothesis involved in the phenomena in question. This is what I shall try to do here, by confining myself to the problems raised by the mediumship of Mlle. Smith, and without entering upon the boundless domain of “psychical research.” I shall, therefore, begin each of the following paragraphs by giving my personal advice and my subjective sentiment on the point upon which Hélène’s supernormal appearances touch.
It seems to me, in the second place, that the only rational position to take, concerning the supernormal, is, if not a complete suspension of judgment, which is not always psychologically possible, at least that of a wise probability, exempt from all dogmatic obstinacy. The fixed beliefs, the unshakable opinions as to the reality and the meaning of life, are certainly subjective conditions, indispensable to all properly moral conduct, to all human existence truly worthy of this name—that is to say, all that which pretends to be above the animal routine of inherited instincts and social slavery. But these firm convictions would be absolutely misplaced on the objective ground of science, and consequently also that of supernormal facts, which, though still situated outside of the scientific realm, hope shortly to be received within its pale. Practical necessities make us but too often forget that our knowledge of the phenomenal world never attains absolute certitude, and as soon as one passes beyond the brutal facts of the senses, the best-established truths, as well as the most thoroughly refuted propositions, do not rise above a probability which, however great or insignificant we may suppose it to be, never equals infinity or zero. The intellectual attitude which common-sense prescribes in the supernormal consists, for very strong reasons, in never absolutely and irrevocably denying or affirming, but provisionally and by hypothesis, as it were. Even in cases when, after having examined everything scrupulously, one imagines he has finally reached certitude, it must not be forgotten that this word is but a mode of expressing one’s self; because, in point of fact, one does not rise above a probable opinion, and the possibility of an unsuspected error, vitiating the most apparently evident experimental demonstration, is never mathematically excluded.