who confidently criticise the actions of captain and pilot, and are anxious to display their ability to form opinions of their own in regard to the intricate navigation over nature's highways. The most efficient antidote to the too ready inclination towards the popular or the superficial interpretation of the phenomena involved in mental telegraphy is doubtless the cultivation of the logical vigor and prudence so frequently referred to; and next to this is an appreciation of the marvelous complexity and unfathomable subtlety of mental operations. THE PSYCHOLOGY OF DECEPTION The saying that appearances are deceptive is an inheritance from ancient times; to Oriental and to Greek philosophers the illusory nature of the knowledge furnished by the senses was a frequent and a fertile theme of contemplation and discussion. The same problem stands open to the psychologist of to-day; but, profiting by the specialization of learning and the advance of technical science, he can give it a more comprehensive as well as a more practical answer. The physiological activities underlying sense-perception are now fairly well understood; the experimental method has extended its domain over the field of mental phenomena; and in many ways have we become more expert in addressing our queries to the sphinx, Nature, so as to force a reply. To outline the position of modern psychology with reference to this interesting problem of deception is the object of the present essay. I In a sense-impression we recognize a primitive element in the acquisition of knowledge. The deprivation of a sense even under most favorable circumstances leaves some traces of an incomplete mental development. This is due, not to the mere sense-impressions that the organ furnishes, but to the perception and coördination of these by inferential processes of a more complex nature. It is not the eye of the eagle, but the brain directing the human eye, that leads to intellectual supremacy. Physiology recognizes this distinction as one between lower and higher brain-centres. A man may have his retina or his optic nerve injured, and so be blind in the ordinary sense of the word. He is prevented from acquiring further knowledge by this avenue; but, unless he become blind in early childhood, he will retain a memory for visual images, will be able more or less clearly to imagine pictorially the appearances of objects from verbal descriptions, and in the free roamings of his dream fancy will live in a world in which blindness is unknown. On the other hand, there is a condition resulting from the disintegration of certain portions of the finely organized cortex of the brain, in which the patient may retain full sight and understanding, but be unable to derive any meaning from what he sees. The same cluster of sensations that enables us to recognize a book, a picture, a face, and to arouse all the numerous associations attaching to these, is as unmeaning to him as the symbols of a cipher alphabet.