There are two general principles, or laws, operative in the processes of Association of Ideas, known as (1) Association by Contiguity; and (2) Association by Similarity, respectively.
Association by Contiguity manifests particularly in the processes of memory. In its two phases of (1) Contiguity of Time; and (2) Contiguity of Space, respectively, it brings together before the field of consciousness ideas associated with each by reason of their time or space relations. Thus, if we remember a certain thing, we find it easy to remember things which occurred immediately before, or immediately after that particular thing. Verbal memory depends largely upon the contiguity of time, as for instance, our ability to repeat a poem, or passage from a book, if we can recall the first words thereof. Children often possess this form of memory to a surprising degree; and adults with only a limited degree of understanding may repeat freely long extracts from speeches they have heard, or even arbitrary jumbles of words. Visual memory depends largely upon contiguity of space, as for instance our ability to recall the details of scenes, when starting from a given point. In both of these forms of association by contiguity the mental operation is akin to that of unwinding a ball of yarn, the ideas, thus associated in the sequence of time or place, following each other into the field of consciousness. Association by Contiguity, while important in itself, properly belongs to the general subject of Memory, and as we have considered it in the volume of this series devoted to the last mentioned subject, we shall not speak of it further here.
Association by Similarity, however, possesses a special interest to students of the particular subject of the culture of the Understanding. If we were compelled to rely upon the association of contiguity for our understanding of things, we would understand a thing merely in its relations to that which went before or came after it; or by the things which were near it in space—we would have to unwind the mental ball of time and space relations in order to bring into consciousness the associated relations of anything. The Association of Similarity, however, remedies this defect, and gives us a higher and broader association. Speaking of Association of Similarity, Kay says: "It is of the utmost importance to us in forming a judgment of things, or in determining upon a particular line of conduct, to be able to bring together before the mind a number of instances of a similar kind, recent or long past, which may aid us in coming to a right determination. Thus, we may judge of the nature or quality of an article, and obtain light and leading in regard to any subject that may be before us. In this way we arrange and classify and reason by induction. This is known as rational or philosophical association."
Halleck says: "An eminent philosopher has said that man is completely at the mercy of the association of his ideas. Every new object is seen in the light of its associated ideas.... It is not the business of the psychologist to state what power the association of ideas ought to have. It is for him to ascertain what power it does have. When we think of the bigotry of past ages, of the stake for the martyr and the stoning of witches, we can realize the force of Prof. Ziehen's statement: 'We cannot think as we will, but we must think as just those associations which happen to be present prescribe.' While this is not literally true, it may serve to emphasize a deflecting factor which is usually underestimated."
Locke says: "The connection in our minds of ideas, in themselves loose and independent of one another, has such an influence, and is of so great force, to set us awry in our actions, as well moral as natural, passions, reasonings, and notions themselves, that, perhaps, there is not any one thing that deserves more to be looked after." Stewart says: "The bulk of mankind, being but little accustomed to reflect and to generalize, associate their ideas chiefly according to their more obvious relations, and above all to the casual relations arising from contiguity in time and place; whereas, in the mind of a philosopher ideas are commonly associated according to those relations which are brought to light in consequence of particular efforts of attention, such as the relations of cause and effect, or of premises and conclusion. Hence, it must necessarily happen that when he has occasion to apply to use his acquired knowledge, time and reflection will be requisite to enable him to recollect it."
This Association by Similarity, or the "rational and philosophical association of ideas," may be developed and cultivated by a little care and work. The first principle is that of learning the true relations of an idea—its various logical associations. Perhaps the easiest and best method is that adopted and practiced by Socrates, the old Greek philosopher, often called "the Socratic method"—the Method of Questioning. By questioning oneself, or others, regarding a thing, the mind of the person answering tends to unfold its stores of information, and to make new and true associations. Kays says: "Socrates, Plato, and others among the ancients and some moderns, have been masters of this art. The principle of asking questions and obtaining answers to them may be said to characterize all intellectual effort.... The great thing is to ask the right questions, and to obtain the right answers." Meiklejohn says: "This art of questioning possessed by Dr. Hodgson was something wonderful and unique, and was to the minds of most of his pupils a truly obstetric art. He told them little or nothing, but showed them how to find out for themselves. 'The Socratic method,' he said, 'is the true one, especially with the young.'"
But this questioning must be done logically, and orderly, and not in a haphazard way. As Fitch says: "In proposing questions it is very necessary to keep in view the importance of arranging them in the exact order in which the subject would naturally develop itself in the mind of a logical and systematic thinker." A number of systems have been formulated by different writers on the subject, all of which have much merit. The following System of Analysis, designed for the use of students desiring to acquire correct associations, was given in the volume of this series, entitled "Memory," and is reproduced here because it is peculiarly adapted to the cultivation and development of the faculty of discovering and forming correct associations and relations between ideas:
SYSTEM OF ANALYSIS
When you wish to discover what you really know regarding a thing, ask yourself the following questions about it, examining each point in detail, and endeavoring to bring before the mind your full knowledge regarding that particular point. Fill in the deficiencies by reading some good work of reference, an encyclopedia for instance; or consulting a good dictionary, or both: