ELEVATION 233 developed to a standard corresponding to his age, by pure and simple demonstration. The importance of such demonstrations was to show that mental facts are susceptible to mathematical measurement. And it included the idea, which was considered almost as an axiom, that the manner of feeling, or rather of perceiving (that is recog- nizing) stimuli was an absolutely natural quality, not dependent on knowledge, or on the methodical working of the mind, or on intellectual education; that is, it was not dependent on those artificial mental differences which result from education. Seeing if one thing is larger or smaller than another, feeling if a minute object has come into contact with our skin* etc. are experiences common to all, and individual differences are characters derived from nature which normally creates its own variations, and which therefore make men more or less sensitive just as they make them more or less intelligent, more or less markedly dark or fair. Its judgments therefore were considered as judgments on the man in his natural mental development. In fact psycho- logy is intended later to determine the characters corresponding to the various mental levels associated with each age and asso- ciated with individual variations (of normal, sub-normal people, etc.). In place of this method, Itard proposed to set up maximum stimuli which were in strong contrast in order to attract to them the sense faculty of children shut out from their environment and incapable of obtaining in the ordinary way precise knowledge of it; he meant to lead them on by repeated exercises, to perceive, step by step, contrasts less abrupt and differences more minute in the separate qualities presented to them. In this case it is not a simple test which is being carried out on the subject in order to demonstrate his mental condition but a modifying action which is directed towards the intelligence in order to awaken it, to kindle contact with the external world, to estimate its characters with precision and to bring into a harmony of interests the intellect and the outer realities.