The questions to which the book is ultimately addressed are:" How do we know? What do we know? When do we know?(p. 1) Almost everywhere, however, what is discussed is belief. The authors' quest is" for empirical criteria for belief in any degree."(p. 2) But it is never made clear whether what the authors are concerned with is the psychology of belief, or the truth or probability of truth of beliefs, or the" value"(in an unstated sense) of beliefs. What puzzles the authors and motivates their inquiry is how it comes about" that a great variety of different and mutually incompatible beliefs are expressed in respect of a subject" to wit, Psychical Research," with a relatively limited bibliography."(p. 2) The authors' main thesis is that" four functions are commonly em-ployed in deriving the sort of knowledge with which we are best satisfied," namely," 1. Logico-deductive synthesis.... 2. Inductive synthesis.... 3. The operational method.... 4. Intuiting, in the sense used by Santayana. Th