Ethics is a science of reactions. Each vocation reacts upon the others. The general reaction of science I have mentioned. In addition the work of the scientist reacts upon agriculture, industry, etc. The industrial arts, as has been stated, are to be regarded as the executive auxiliaries of science, receiving from it the knowledge of the uniformities of nature, and in turn setting for science new problems by attention to which scientific theory is advanced. The relations of science to art also need to be considered at greater length than is possible here. I have in mind inquiries into the scientific basis of music like those of Helmholtz, the scientific theory of color and the like, and also detailed studies of the return gift which art confers on science, especially the value to the scientist of that cultivation of the imagination which is gained by the contemplation and study of works of art. There are different kinds of imagination: the purely artistic, the scientific, the mechanical imagination, the ethical imagination. The function of the imagination in advancing science has been discussed by Tyndall and others, but the subject is far indeed from being exhausted. The scientist then may be defined as one who stands in reciprocal relations to all other departments of human interest and activity, who gives to each from his specific standpoint as a scientist, and receives from each, from religion,[75] from art, from the practical vocations, etc. Ideally speaking, every man participates in all the principal interests and activities of the human mind. Every man is something of an artist, something of a practical or executive worker, scientist, religious being. But in each individual the different interests are colored by his special pursuit, and the influence he wields in return is modified in the same fashion.[76] There are three great tasks that occupy human life: 1. To build our finite world (science and its adjuncts). 2. To create in the finite the semblance of the infinite, or spiritual relation (art). 3. To strive to realize the spiritual relation in human intercourse (ethics and religion). This discussion of science affords me the opportunity to give an exact definition of the word “instrumental” as I use it. And the word “instrumental” is of decisive importance as to the entire ethical conception of life. Instrumental in what sense? The finite ends of man are to be the means used in the pursuit of the infinite end. But in what manner are they to be the means? To be a _cheerful world-builder_, to take an active and whole-hearted interest in the improvement of material conditions, in political reforms, in the embellishment of earthly life—how is it possible to do this and at the same time keep the spiritual end in view as the supreme end?