“In discussing matters of this kind, two rules are to be observed, as Augustine teaches (Gen. ad litt. i). The first is to hold the truth of Scripture without wavering. The second is that since Holy Scripture can be explained in a multiplicity of senses, one should adhere to a particular explanation only in such measure as to be ready to abandon it, if it be proved with certainty (certa ratione) to be false, lest Holy Scripture be exposed to the ridicule of unbelievers, and an obstacle be placed to their believing (Ia Qu. 68, Art. 1, Eng. Tr.).

“As, however, this theory (i.e. an infinite body of waters beyond the heavens) can be shown to be false by solid reasons (per veras rationes), it cannot be held to be the sense of Sacred Scripture. It should rather be considered that Moses was speaking to ignorant people (rudi populo) and that out of condescension to their weakness he put before them only such things as are apparent to sense” (ibid., Art. 3).