From the Preface.
The main purpose of our existence on earth — aside from the sacred and paramount duty of securing our salvation — is undoubtedly to make ourselves masters of the tangible world around us, as it stands revealed to our senses, and as it was expressly made subject to our will by the Creator. We are, however, at the same time, not left without information about the existence of certain laws and the occurrence of certain phenomena, which belong to a world not accessible to us by means of our ordinary senses, and which yet affect seriously our intercourse with Nature and our personal welfare. This knowledge we obtain sometimes, by special favor, as direct revelation, and at other times, for reasons as yet unknown, at the expense of our health and much suffering...
...There are, it is well known, many theologians who sternly deny any such further development of man's spiritual part, and insist upon looking at this life as the only time of probation accorded to him, at the end of which immediate and eternal judgment is rendered. Their views are entitled to the utmost consideration and respect. But different opinions are entertained by some of their brethren, not less eminent in piety, profound learning, and critical acumen, and hence at least equally deserving of being attentively listened to and carefully regarded. So it is also with the belief in the possibility of holding intercourse with disembodied spirits. Superficial observers are ready to doubt or to deny, to sneer haughtily, or to scoff contemptuously. But men of great eminence have, from time immemorial, treated the question with great attention and deep interest. Melanchthon wrote: "I have myself seen ghosts, and know many trustworthy people who affirm that they have not only seen them, but even carried on conversations with them" (De Anima Recogn.: Wittemb. 1595, p. 317)....
