He who pronounces anything to be "impossible," outside of the field of pure mathematics, is wanting in prudence.
Francois Arago.
A learned pedant who laughs at the possible comes very near being an idiot. To purposely shun a fact, and turn one's back upon it with a supercilious smile, is to bankrupt Truth.
Victor Hugo.
Science is under bonds, by the eternal principles of honor, to look fearlessly in the face every problem that is presented to her.
Sir William Thompson.
PREFACE
The subject treated in the following pages has made great progress in the course of forty years. Now what we are concerned with in psychical studies is always unknown forces, and these forces must belong to the natural order, for nature embraces the entire universe, and everything is therefore under the sway of her sceptre.