Page:Popular Science Monthly Volume 77.djvu/548

542 one of his university teachers, Knutzen, professor of logic and metaphysics at Koenigsberg, who was at once an ardent Pietist, an ardent Wolffian, and an ardent Newtonian. All of the earliest three considerable writings of Kant may be said to be chiefly attempts to give new applications to Newton's principles, or to supply his omissions, or to do both at once. Of these three, the treatise with which we are here concerned, the "Allgemeine Naturgeschichte" of 1755, was an endeavor to fill up two of the most obvious gaps (from the cosmical system-maker's point of view) which the author of the "Principia" had left. It required no great originality and no stroke of genius on Kant's part to recognize these gaps and to devise the general outlines of the hypotheses by which he tried to fill them. The problems, and in one of the two cases at least, the proposed solution even in most of its details, were present in the scientific atmosphere of the period as epidemic infections.

The first of these gaps, and the one less pertinent to our present topic, lay in Newton's failure to suggest even a conjectural hypothesis concerning the systematic arrangement of the heavenly bodies beyond the boundaries of our system. To three of his disciples at almost the same time —but to the two others at an earlier date than to Kant—it occurred as a "probable," though perhaps not strictly verifiable, supposition that our group of planets with its central sun is only a part of an analogous but larger concentric system of revolving bodies, or of similar groups of bodies, constituting the Milky Way; and that this in turn is but part of a single, universal system, all the members of which are similarly arranged with respect to one another, and revolve about a body at the center of gravitation of the entire universe in accordance with Newton's laws. The hypothesis had, of course, an attractive combination of grandiosity and simplicity; and it was natural enough to inquire whether or not it were true. But it was, I suppose, essentially incapable of any serious testing by any data then in the possession of astronomers. It is apparently only within the past five years that some light has been thrown upon the problem of a possible "systematic arrangement" of the fixed stars; and the arrangement which recent