People are not the only interesting organism on earth. From the point of view of scientific or commercial value, there are lots of interesting organisms. ↗
The powers, aspirations, and mission of man are such as to raise the study of his origin and nature, inevitably and by the very necessity of the case, from the mere physiological to the psychological stage of scientific operations. ↗
From all this it follows what the general character of the problem of the development of a body of scientific knowledge is, in so far as it depends on elements internal to science itself. ↗