St. Thomas Held and Taught that the Earth is Round
To the Editor, The Ecclesiastical Review.
In his beautiful pageant The Discovery of America Dr. Coakley introduces Columbus as saying to the prior of La Rabida
"... My studies prove that our dwelling place is round ".
To which the gentle friar answers ("in great surprise"),
"You say 'tis round !"
And then Columbus :
"As round as is the ball beneath yon towering cross ".
Afterward, in the court scene when Isabella is told that Columbus
holds the earth to be round, she is greatly amazed, and even the
Cardinal shakes his head dubiously.Now while the surprise of the Queen at hearing a cosmical theory which may not have passed from the University hall into the palace, was natural enough, a prince of the Church and the prior of a monastery ought not to have been unaware of the opinion held by many of the learned of their day that this earth of ours is really a sphere. For were not St. Thomas's Summa Theologica as well as Aristotle's Physics text-books at the time in the hands of university professors and students?
In both these familiar instruments of knowledge the sphericity of the earth is explicitly maintained. The Angelic Doctor mentions the subject in two passages of the Summa (P. I, Q. I, A. I, ad 2um, and P. I-II, Q. LIV, A. 2 ad 2um) ; also in his commentary on the Sentences (II, D, 24, Q. 2, 2, 5um) ; in his commentary on the Post. Anal. (L. 41), on the Phys. (II, L. 3) ; and more at length in the De Coelo et Mundo (L. II, L. 26, 27, 28). One citation from the Summa will suffice for the present purpose.
St. Thomas is answering an objection against his conclusion that the principle upon which habits are classified is their formal object. It is urged that one and the same object may fall under different habits of science; "sicut terram esse rotundam demonstrat naturalis et astrologus". He replies : "Dicendum quod terram esse rotundam per aliud medium demonstrat naturalis, et per aliud astrologus. Astrologus enim hoc demonstrat per media mathematica, sicut per figuras eclipsium, vel per aliud hujusmodi. Naturalis vero hoc demonstrat per medium naturale, sicut per motum gravium ad medium, vel per aliud hujusmodi." And the rest (I, Q. LIV, A. 2 ad 2um).
In other words, St. Thomas declares that Aristotle's assertion that the earth is round is capable of proof by two middle terms. The astronomer derives his argument from mathematics, that is, from the round shape of the earth cast upon the disk of the moon during an eclipse. The natural philosopher derives his argument from the physical phenomenon of gravitation, namely that "heavy" bodies tend toward the centre of the earth; therefore the earth must be round.
That the roundness here meant is certainly not that of a flat disk, but that of a ball or sphere is abundantly manifest from the teaching both of Aristotle and of Aquinas which is developed at some length in the Lectiones (26, 27, 28) on the second book of the De Coelo et Mundo.
Moreover, both these venerable teachers thought it probable that the ocean stretching beyond Gibraltar merged into the Mare Indicum, which washed the eastern shores of India; and since this opinion was laid down in the second book of the Philosopher's De Coelo et Mundo, commented upon by Aquinas (Lect. 28), it is not so surprising that the great Genoese thought the earth was round and that by sailing westward from the pillars of Hercules he would reach the shores of India; or that until his death Columbus believed that he had actually landed upon the Asian continent. The surprise is that the ecclesiastics of his day are thought not to have known the teachings of their school books.
J. F. S.
