In using words, all we have to do is to _convey our meaning_, either by description or illustration, and when we have done this, to select a word to express it; and that word is best for this purpose which would recall this meaning to the greatest number of persons who have previously used it in this sense. For this reason, it is most proper to use terms employed in common life to express the phenomena treated of in mental science, instead of instituting new terms, which, to most persons, have never had the intended ideas connected with them. This method is adopted in the following pages; but it is important to remember that, while these words are used both in common life and by metaphysical writers with the meaning here indicated, they are often used with other significations. Thus the word _to perceive_ is used not only to signify the act of gaining ideas by the senses, but any act of mind in noticing truths of any kind, either mental or external. So _to conceive_ and _to perceive_ are often used interchangeably as meaning the same thing. But this does not render it necessary to seek any new terms to express these ideas. All that is needful is to indicate that in classing and describing mental phenomena we restrict ourselves to one exact and uniform use of these terms, and this use is indicated in the description or definition given. CHAPTER VIII. CLASSIFICATION AND DESCRIPTION OF THE MENTAL POWERS. We now proceed to the classification and description of the mental powers. Not only all writers on mental science, but the most common writers and speakers, recognize a general division of mental operations, which is expressed by the terms _intellect_, _feeling_, and _choice_. We _think_, we _feel_, and we _choose_. Even the young child learns to comprehend these three grand divisions of the mental phenomena. To this most general division, in this work, are applied the terms _the intellectual powers, the susceptibilities_, and _the will_. These terms are selected because they are the most common ones. THE INTELLECTUAL POWERS. Under the general class of intellectual powers are arranged the following specific powers of mind: Sensation, Perception, Conception, Memory, Imagination, Judgment, Abstraction, Attention, and Association. _Sensation_ is a state of mind produced by material objects acting on the senses. Thus, when light, which is considered as one kind of matter, affects the eye, the sensation of _sight_ is produced. When the perfume of a rose, which is another species of matter, affects the nostrils, the sensation of _smell_ is produced. When a bell or some musical instrument causes the air to vibrate on the drum of the ear, it causes the sensation of _sound_. When any sapid body is applied to the tongue, the sensation of _taste_ is caused. When the hand, or any part of the body, comes in contact with another body, the sensation of _touch_ is produced.