Startling as it may appear, there have been in this century quite a few first-rate astronomer-cosmologists who professed themselves to be solipsists or at least idealists in the Kantian sense. They were never so consistently idealist as to miss an opportunity to clamor for better and bigger telescopes, although they seized on any opportunity to reduce stars to a mere sensation on their retinae. Chesterton not only was immune to such philosophical bungling, but he was also the first-rate philosophical cosmologist who instinctively made the proper improvement right there where some of the best philosophers went wrong in cosmology. I doubt that Chesterton ever read Book Lambda of Metaphysics, where the pantheist Aristotle roundly declared that the universe is a house without a master, or an army without a commander. Chesterton's universe explicitly had a captain and a "divine captain" at that, and this is why it had a Flag.
[SLJ Chesterton a Seer of Science 98]
Here are the relevant footnotes:
 As argued by Professor William H. McCrea during a conference on "Cosmology, History and Theology" at the University of Denver, November 5-8, 1974. He was considerably taken aback by my question, whether the wall facing him was also a mere sensation on his retina.
 Aristotle, Metaphysics, 1074b-75b. Such was both the capstone and very source of that cosmic necessitarianism which put science into a straitjacket for
almost two thousand years; that is, until some basic points of Aristotelian cosmology wore rejected by medieval Scholastics, guided by the dictates of their Christian faith in creation out of nothing and in time.
 This is the argument of ch. 5, "The Flag of the World," in [GKC's] Orthodoxy.