It is not always becoming to entertain one’s readers with personalities, but I think I ought to infringe a little upon decorum, in order to specify the state of mind in which I have pursued my observations. From the very beginning I was struck by a fact which seems beyond doubt. I saw that certain manifestations—to all appearances supernormal—could only be studied with the assistance of nervous and mental pathology. Therefore I went to school again, and for six years I studied assiduously clinical medicine at the University of Bordeaux. It is not within my present scope to write the panegyric of the masters to whose teachings I listened, their names would seem out of place in a book like this. But I may say that the interest which I took in my medical studies became more lively, as I understood their importance better and better. Doubtless the notions which I have acquired are most rudimentary, but however unpretentious they may be, they have enabled me to understand the mechanism of certain manifestations, and to bring a more precise judgment to bear upon their psychological value. I am, therefore, an interested but impartial onlooker. It matters little to me if a table or a chair moves of its own accord; I have no particular desire to see them accomplish these movements. The only interest, which I find in this fact, is its truth. Its reality alone is of value to me, and I have applied myself to establish this without any possible error. My unique preoccupation has been to make sure of the reality of the phenomena which I observed. The pursuit of truth has been my sole concern. True, I sought it in my own way; for I preferred to build my conviction upon a basis which would satisfy my intelligence and my reason, rather than impose _a priori_ conditions which the experiment ought to satisfy in order to convince me. I am ignorant of most of these conditions, and I think that every one else is also. Consequently, I consider it imprudent to establish beforehand the conditions under which the experiments are to be made, in order to merit being recorded. It might just happen, that one of the conditions thus laid down rendered the experiment impracticable. Therefore I have observed rather than experimented. My manner of proceeding has been productive of many happy results; for the curious phenomena which I have been able to observe are capricious; they shun those who would force them, and offer themselves to those who wait for them patiently. This behaviour, this spontaneity, is not the least astonishing feature in this line of observation.