The Encyclopaedia and Dictionary of Education; A Comprehensive, Practical and Authoritative Guide on All Matters Connected with Education, Including Educational Principles and Practice, Various Types of Teaching Institutions, Volume 2 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1921 edition. Excerpt: ...terms hallucination and illusion is based upon the fact that an illusion is a misinterpretation of a sensation produced by an object actually present to the senses, while an hallucination is a false perception in which the origin of the stimulus is either organic or imaginative. In practice, however, it is impossible to draw a distinct line between the two. In an hallucination there is often some slight external stimulus which gives rise to the subjective conditions producing it, while an illusion frequently contains some of the elements of an hallucination. Both hallucinations and illusions are classified according to the sense organ affected. Illusions are common to all the sense organs, while hallucinations are chiefly found in connection with the senses of sight and hearing. There are also motor illusions and hallucinations in which the idea of movement is the predominant factor. Pure illusions (i.e. those in which no element of hallucination is present) may be collective, but it is very doubtful whether any evidence of collective hallucination exists. Hallucinations and illusions are specially characteristic of certain forms of insanity, of various disorders of the nervous system, and of the action of special drugs. Dream experiences are to a large extent illusions, while hypnotic phenomena partake more of the character of pure hallucination. Both forms are found in normal persons, but in these illusion is much more common, and is more often than not produced by a predisposition to apperceive a presentation in a certain way. Aristotle's historic experiment in which an object placed between the crossed first and second fingers appears double, well illustrates such a case. Here in their normal position the outer side of one finger and inner...