This matter of association by relation is one of the most important things in the whole subject of thought, and the degree of correct and efficient thinking depends materially upon it. It does not suffice us to merely "know" a thing—we must know where to find it when we want it. As old Judge Sharswood, of Pennsylvania, once said: "It] is not so much to know the law, as to know where to find it." Kay says: "Over the associations formed by contiguity in time or space we have but little control. They are in a manner accidental, depending upon the order in which the objects present themselves to the mind. On the other hand, association by similarity is largely put in our own power; for we, in a measure, select those objects that are to be associated, and bring them together in the mind. We must be careful, however, only to associate together such things as we wish to be associated together and to recall each other; and the associations we form should be based on fundamental and essential, and not upon mere superficial or casual resemblances. When things are associated by their accidental, and not by their essential qualities,—by their superficial, and not by their fundamental relations, they will not be available when wanted, and will be of little real use. When we associate what is new with what most nearly resembles it in the mind already, we give it its proper place in our fabric of thought. By means of association by similarity, we tie up our ideas, as itwere, in separate bundles, and it is of the utmost importance that all the ideas that most nearly resemble each other be in one bundle."