The importance of correct powers of Abstraction is seen when we realize that all concepts or general ideas are but combinations of abstract qualities or ideas. As Halleck says: "The difference between an _abstract idea_ and a _concept_ is that a concept may consist of a bundle of abstract ideas. If the class contains more than one common quality, so must the concept; it must contain as many of these abstracted qualities as are common to the class. The concept of the class _whale_ would embody a large number of such qualities." As Brooks says: "If we could not abstract, we could not _generalize_, for abstraction is a condition of generalization." The last-mentioned authority also cleverly states the idea as follows: "The products of Abstraction are _abstract ideas_, that is, ideas of qualities in the abstract. Such ideas are called _Abstracts_. Thus my idea of some particular color, or hardness, or softness, is an abstract. Abstract ideas have been wittily called 'the ghosts of departed qualities.' They may more appropriately be regarded as the spirits of which the objects from which they are derived are the bodies. In other words, they are, figuratively speaking, 'the disembodied spirits of material things.'" The cultivation of the faculty of Abstraction depends very materially, in the first place, upon the exercise of Attention and Perception. Mill holds that Abstraction is primarily a result of Attention. Others hold that it is merely the mental process by which the attention is directed exclusively to the consideration of one of several qualities, properties, attributes, parts, etc. Hamilton says: "Attention and Abstraction then are only the same process viewed in different relations. They are, as it were, the positive and negative poles of the same act." The cultivation of Attention is really a part of the process of the cultivation of the faculty of Abstraction. Unless the Attention be directed toward the object and its qualities we will be unable to perceive, set aside, and separately consider the abstract quality contained within it. In this process, as indeed in all other mental processes, Attention is a prerequisite. Therefore, here, as in many other places, we say to you: "Begin by cultivating Attention."