The father of it was Aristotle. His conception of the universe rested upon the plain contrast, which strikes the unsophisticated observer, between the unembarrassed and regular movements of the heavenly bodies and the disordered agitations of sublunary things. Hence the heavenly region was eternal, and the region of earth transitory: yonder, the motions that take place are eternal and regular; here, motion and rest alternate, nothing "continueth in one stay."
At the centre of the universe stands Earth: hence we mount through three sublunary strata to the region of the celestial ether, which is purer as distance from the Earth increases.
These strata form three concentric "spheres" which, solid yet transparent (like crystal), revolve around the earth. The first contains the moon—like a fly in amber; the second, the sun; the third, the fixed stars; which last sphere is also the first of several successive heavens, the highest of which is the seat of Deity.
This Aristotelio-Ptolemaic system[2] formed a coherent framework for biblical world-notions. Here too, earth stands still while sun and stars revolve; here, too, the seat of Deity is the highest heaven. This was an universe where men could feel their feet on firm ground; their minds found rest in those simple and definite notions which make religious conceptions easy to understand and accept; their imaginations were not yet disturbed and disquieted by thoughts of space and time without end and without beginning.
Aquinas.—Such was the "world of nature," the theatre for that "world of grace" which Revelation spoke of, and which led eventually to the eternal "world of glory" in which the faithful should have their portion. Natura, gratia, gloria was the ascending series (like another set of celestial spheres), and the whole economy was elaborated into a logical system, known to the historians of thought as Scholasticism: a philosophy which found its most perfect and memorable expression in Thomas Aquinas (1227-74), the doctor angelicus of Catholic theology, canonised less than fifty years after his death. The Summa Philosophica, where Aquinas deals with the rational foundations of a Christian Theism, and the Summa Theologica, where he erects his elaborate structure of theology and ethics, together constitute "one of the most magnificent monuments of the human intellect, dwarfing all other bodies of theology into insignificance."[3] In him the erudition of an epoch found its spokesman; he was the personification of an intellectual ideal. To his contemporaries he stood beyond the range of criticism. In the Paradiso (x.8.2) it is St. Thomas who speaks in heaven.
Nevertheless, the Scholastic world-scheme, though based on "the evidence of the senses, the investigations of antiquity, and the authority of the Church," and though Aquinas had set the seal of finality upon it, was destined to gradual discredit and ultimate extinction.
Disintegration Begins.—It was open to attack on two sides. Either observations or calculations might be brought forward, conflicting with it, or making another conception possible or probable: Or the validity of conventional ideas of space might be disputed.
The latter type of criticism was the first to occur. Nicholas Cusanus (1401-1464), an inhabitant of the Low Countries, subsequently bishop and cardinal, developed unconventional notions about Space. He suggested that wherever man finds himself—on earth, sun, or star—he will always regard himself as standing at the centre of existence. There is, in fact, no point in the universe which might not appropriately be called its centre, and to say that the earth stands at the centre is only (what we should now call it) an anthropomorphism. So much for place; and similarly with motion. Here, too, there is no absolute standard to apply: motion may exist, but be unnoticed if there be no spot at absolute rest from which to take bearings.
"We are like a man in a boat sailing with the stream, who does not know that the water is flowing, and who cannot see the banks: how is he to discover whether the boat is moving?" Cusanus, in fact, denies the fundamental Aristotelian dogma that the earth is the central point of the universe, because, on general grounds, there can be no absolute central point. This gave a shock to the "geocentric theory" from which it never recovered.
Worse shocks, however, were to come. The name of the man who actually (as Luther complained) turned the world upside down, is notorious enough. Poles and Germans alike have claimed the nationality of Nicolaus Copernicus (1473-1543); who, having been a student at Cracow and in Italy, became a prebendary in Frauenburg Cathedral.