Each science has a different subject-matter. It will, perhaps, help to emphasize the importance of this inquiry if we recall, first, that a science presupposes the existence of a special kind of material, called its subject-matter; and, second, that each science has a different subject-matter. For example, in geology we learn about the structure of the earth’s surface; in physiology, about the functions of living organisms. Physics is a study of bodies in motion; and geometry, of figures and space. In these, and in similar cases, the subject-matter of the science is the material which the scientist observes and describes… At present, we wish to call the student’s attention to the fact that the attainment of any kind of knowledge is impossible without an active exercise of the thinking processes, and to warn him that the passive flow of images and ideas through consciousness must not be mistaken for thinking. It is true that without images and ideas there can be no thought; but thinking consists in comparing objects with one another, in differentiating the like from the unlike, in combining them into more complex wholes, in relating in many and diverse ways these wholes to each other, etc. Thinking, in other words, is a specialised sort of mental activity, an activity that taxes to the utmost, and frequently brings into play, all the abilties with which the human mind is endowed. It is the supreme task to which the many have been called; but if we regard it lightly, or presume that it can be accomplished without toil, or if we erect our own incapacity or indolence into a reason for the uselessness of the endeavor, we must abandon the hope of joining the company of the few who are chosen. It is, therefore, with good reason that logic directs attention to the function of thought in human knowledge, for thinking is the one way, the only royal road, to the goal of an educated life. To think about the objects of one’s experience is, then, necessary if knowledge is to exist; but thinking, it must also be borne in mind, is “not a passive suffering of something, but a doing of something with” these objects.