In reading this book we may begin to see that there is nothing "unnatural" in the hypothesis that there may be reports conveyed to the consciousness of man by means of higher vibrations than those of ordinary sound, or ordinary sight, providing that man has either highly developed his ordinary senses of sight, hearing, or touch to a degree sufficiently high to register these higher vibrations; or else has evolved and unfolded into consciousness certain latent faculties of sense-impression which are lying dormant in the great masses of mankind. In fact, the thoughtful person will be forced to admit that this new knowledge of the nature of sensations, and of its relation to vibratory motion, renders extremely probable the truth of the great body of reports of such so-called extra-conscious knowledge which the experience of the race has furnished from the beginning of human history down to the present time. Such a person will see that it is not a sign of "credulity" for a person to accept such reports, so universally set forth; but that, rather, it is a sign of "credulity" for a person to accept blindly the dogmatic assertions of the materialistic sceptics to the effect that "there is no such thing possible in the natural world, under natural world, under natural laws - the whole thing is delusion or else deliberate fraud." Such "know-it-all" persons are usually found to really "know much that is not true," and to lack knowledge of much that is true, regarding Nature, her realm and her laws.

Let us say that the student of this book will find nothing contained within this book which is contrary to Nature's laws and principles. He will nowhere in it be asked to suspend the exercise of his reason, and to accept as facts things which violate all of Nature's laws. Instead, he will find at each point full natural explanations of even the most wonderful phenomena; and the appeal to accept same will be made always to his reason, and not to his blind faith or unreasoning belief. The student is urged to build his knowledge of this important subject upon this solid rock of natural law and fact, and not upon the shifting and sinking sands of mere dogmatic assertion and appeal to assumed authority ancient or modern.