. . . the nature of the mind presents the fundamental problem, perhaps the most difficult and most important of all problems. For myself, after a professional lifetime spent in trying to discover how the brain accounts for the mind, it comes as a surprise now to discover, during this final examination of the evidence, that the dualist hypothesis seems the more reasonable of the two possible explanations [the other being that the brain explains the mind]. . . . What a thrill it is, then, to discover that the scientist, too, can legitimately believe in the existence of the spirit. (Wilder Penfield)