§ 21. Inquiries like these, though they may appear at first to degrade great truths or solemn conceptions, are likely to end by exalting and affirming them. lxx–lxxi

ADDITIONS AND CORRECTIONS . . . . . . . lxxiii–lxxx

CHAPTER I.

PRELIMINARY REMARKS: GROUNDS OF CAUTION.

§ 1. The great test of scientific achievement is often held to be the power to predict natural phenomena; but this test, though authoritative in the sciences of inorganic nature, has only a limited application to the sciences that deal with life, and especially to the department of mental phenomena. 1–3

§ 2. In dealing with the implications of life and the developments of human faculty, caution needs to be exercised in two directions. The scientist is in danger of forgetting the unstable and unmechanical nature of the material, and of closing the door too dogmatically on phenomena whose relations with established knowledge he cannot trace. Others take advantage of the fact that the limits of possibility cannot be scientifically stated here, to gratify an uncritical taste for marvels and to invest their own hasty assumptions with the dignity of laws. 3–5

§ 3. This state of things subjects the study of “psychical” phenomena to peculiar disadvantages and imposes peculiar obligations upon the student. 5–6

§ 4. This should be well recognized by those who advance a conception so new to psychological science as the central conception of this book—to wit, Telepathy, or the ability of one mind to impress or to be impressed by another mind otherwise than through the recognized channels of sense. (Of the two persons concerned, the one whose mind impresses the other will be called the agent, and the one whose mind is impressed the percipient.) 6–7

§ 5. Telepathy will be studied here chiefly as a system of facts, with theoretical discussion subordinated to the presentation of evidence. The evidence will be of two sorts—spontaneous occurrences and the results of direct experiment—the latter of which must be carefully distinguished from spurious “thought-reading” exhibitions. 7–9