The empirical interest is the mental eagerness aroused by direct appeal to the senses, as by novel shapes, colors, sounds, odors, and the like. Its first stage is wonder, admiration, fear, awe. The child that drops his picture-book to chase a butterfly abandons one empirical interest for a stronger one. This form of interest is usually transient; unless it develops into a new kind of interest, it is soon abandoned for some other attraction. A primary teacher may catch but cannot hold the attention of a child by sensuous devices leading to nothing beyond themselves. The speculative interest is more permanent than the empirical. It rests primarily on the perception of the relations of cause and effect; it seeks to know the reasons of things. On this account it is a higher form of apperception, or mental assimilation. The most fundamental idea in the speculative interest is that of purpose. We want to know the _purpose of things_, the function they are to perform, the end they are expected to reach. Thus a child has a key to the understanding of even so complicated a machine as a self-binder, or a printing press, provided he sees clearly the purpose of each. Until this is perceived the facts are an unintelligible jumble of particulars. A crude form of the speculative interest is seen very early in the child, when he demands a reason for everything. It always remains the mainspring of intellectual life; when it ceases to be a motive power to thinking, thought is dead. The æsthetic interest rests upon the enjoyment of contemplation, when an _ideal_, sometimes distinct, sometimes vague, can be perceived through a _sense medium_. In the Greek statue of _Apollo Belvidere_, a divinity is represented in marble. In the painting, _Breaking Home Ties_, the feelings of a lad and his mother upon parting are portrayed upon canvas. In music the ideal is usually vague, in poetry it is clear and distinct. The æsthetic value of the latter is enhanced by good oral recitation, both because appeal is made to an additional sense, and because the ears of men were attuned to beautiful poetry long before the eye learned to apprehend it.