I readily admit that many, who turn their attention to the curious phenomena of which I am going to speak, frequently lay themselves open to criticism. Sometimes they are not very strict concerning the conditions under which their experiments are conducted: they trust naïvely, and their conviction is quickly formed. I cannot too forcibly beg them to be on their guard against premature assertions: may they avoid justifying Montaigne’s saying, ‘L’imagination crée le cas.’ My remark is more particularly addressed to occult, theosophical, and spiritistic groups. The first-named follow an undesirable method. Their manner of reasoning is not likely to bring them many adepts, from among those who are given to thinking deeply. In ordinary logic, analogy and correspondence have not the same importance as deduction and induction. On the other hand it does not seem to me prudent to consider the esoteric interpretation of the Hebrew writings as being necessarily truth’s last word. I do not see why I should transfer a belief in their exoteric assertions to a belief in their talmudistic or kabbalistic commentaries. I can hardly believe that the Rabbis of the middle ages, or their predecessors, Esdras’ contemporaries, had a more correct notion of human nature than we have. Their errors in physics are not valid security for their accuracy in metaphysics. Truth cannot be usefully sought in the analysis of a very fine but very old book: all occult speculations upon secret hebraic exegeses seem to me but intellectual sport, to the results of which the words of Ecclesiastes might well be applied: _Habel habalim vekol habel_. I may pass the same criticism upon theosophists. The curious mystical movement to which the teachings of Madame Blavatsky, Colonel Olcott, and Mrs. Besant have given birth in Europe and in America has not yet been arrested. Many cultured minds and refined intelligences have allowed themselves to be led away by the neo-buddhistic evangile; doubtless they find what they look for in the ‘Secret Doctrine’ or in ‘Isis Unveiled.’ _Trahit sua quemque voluptas._ I cannot help thinking that the Upanishads have no more a monopoly of truth than the Bible has, and that every philosophy ought to hold fast to the study of Nature if it wishes to live and progress. This is, moreover, the advice of a man whom theosophists and occultists alike respect—I mean Paracelsus—‘Man is here below to instruct himself in the light of Nature.’