The curfew tolls the knell of parting day,
The lowing herd winds slowly o'er the lea,
The ploughman homeward plods his weary way
And leaves the world to darkness and to me;
the words of the author suggest a problem to the mind of the reader. This problem then calls up in the mind of the student a set of images out of earlier experience, as bell, evening, herd, ploughman, lea, etc., which the mind unifies into the representation of the particular scene depicted in the lines. It is in this way that much of our knowledge of various objects and scenes in nature, of historical events and characters, and of spiritual beings is obtained.
Imagination Gives Basis for Generalization.—It should be noted by the student-teacher that in many lessons we aim to give the child a notion of a class of objects, though he may in actual experience never have met any representatives of the class. In geography, for instance, the child learns of deserts, volcanoes, etc., without having experienced these objects through the senses. It has been seen, however, that our general knowledge always develops from particular experience. For this reason the pupil who has never seen a volcano, in order to gain a general notion of a volcano, must first, by an act of constructive imagination, image a definite picture of a particular volcano. The importance of using in such a lesson a picture or a representation on a sand-board, lies in the fact that this furnishes the necessary stimulus to the child's imagination, which will cause him to image a particular individual as a basis for the required general, or class, notion. Too often, however, the child is expected in such lessons to form the class notion directly, that is, without the intervention of a particular experience. This question will be considered more fully in [Chapter XXVII], which treats of the process of imagination.
C. LEARNING BY INFERENCE, OR DEDUCTION
Instead of placing himself in British Columbia, and noting by actual experience that there is a large rainfall there, a person may discover the same by what is called a process of inference. For example, one may have learned from an examination of other particular instances that air takes up moisture in passing over water; that warm air absorbs large quantities of moisture; that air becomes cool as it rises; and that warm, moist air deposits its moisture as rain when it is cooled. Knowing this and knowing a number of particular facts about British Columbia, namely that warm winds pass over it from the Pacific and must rise owing to the presence of mountains, we may infer of British Columbia that it has an abundant rainfall. When we thus discover a truth in relation to any particular thing by inference, we are said to go through a process of deduction. A more particular study of this process will be made in [Chapter XXVIII], but certain facts may here be noted in reference to the process as a mode of acquiring knowledge. An examination will show that the deductive process follows the ordinary process of learning, or of selecting certain elements of old knowledge, and organizing them into a new particular experience in order to meet a certain problem.
Deduction as Formal Reasoning.—It is usually stated by psychologists and logicians that in this process the person starts with the general truth and ends with the particular inference, or conclusion, for example:
Winds coming from the ocean are saturated with moisture.
The prevailing winds in British Columbia come from the Pacific.
Therefore these winds are saturated with moisture.
All winds become colder as they rise.