"Usually, even a non-Christian knows something about the earth, the heavens, and the other elements of this world, about the motion and orbit of the stars and even their size and relative positions, about the predictable eclipses of the sun and moon, the cycles of the years and the seasons, about the kinds of animals, shrubs, stones, and so forth, and this knowledge he holds to as being certain from reason and experience. Now, it is a disgraceful and dangerous thing for an infidel to hear a Christian, presumably giving the meaning of Holy Scripture, talking nonsense on these topics; and we should take all means to prevent such an embarrassing situation, in which people show up vast ignorance in a Christian and laugh it to scorn. The shame is not so much that an ignorant individual is derided, but that people outside the household of faith think our sacred writers held such opinions, and, to the great loss of those for whose salvation we toil, the writers of our Scripture are criticized and rejected as unlearned men. If they find a Christian mistaken in a field which they themselves know well and hear him maintaining his foolish opinions about our books, how are they going to believe those books in matters concerning the resurrection of the dead, the hope of eternal life, and the kingdom of heaven, when they think their pages are full of falsehoods on facts which they themselves have learnt from experience and the light of reason? Reckless and incompetent expounders of Holy Scripture bring untold trouble and sorrow on their wiser brethren when they are caught in one of their mischievous false opinions and are taken to task by those who are not bound by the authority of our sacred books. For then, to defend their utterly foolish and obviously untrue statements, they will try to call upon Holy Scripture for proof and even recite from memory many passages which they think support their position, although they understand neither what they say nor the things about which they make assertion [(1 Tim 1:7)]."
"Plerumque enim accidit ut aliquid de terra, de coelo, de caeteris mundi huius elementis, de motu et conversione vel etiam magnitudine et intervallis siderum, de certis defectibus solis ac lunae, de circuitibus annorum et temporum, de naturis animalium, fruticum, lapidum, atque huiusmodi caeteris, etiam non christianus ita noverit, ut certissima ratione vel experientia teneat. Turpe est autem nimis et perniciosum ac maxime cavendum, ut christianum de his rebus quasi secundum christianas Litteras loquentem, ita delirare audiat, ut, quemadmodum dicitur, toto coelo errare conspiciens, risum tenere vix possit. Et non tam molestum est, quod errans homo deridetur, sed quod auctores nostri ab eis qui foris sunt, talia sensisse creduntur, et cum magno eorum exitio de quorum salute satagimus, tamquam indocti reprehenduntur atque respuuntur. Cum enim quemquam de numero Christianorum in ea re quam optime norunt, errare comprehenderint, et vanam sententiam suam de nostris Libris asserere; quo pacto illis Libris credituri sunt, de resurrectione mortuorum, et de spe vitae aeternae, regnoque coelorum, quando de his rebus quas iam experiri, vel indubitatis numeris percipere potuerunt, fallaciter putaverint esse conscriptos? Quid enim molestiae tristitiaeque ingerant prudentibus fratribus temerarii praesumptores, satis dici non potest, cum si quando de prava et falsa opinatione sua reprehendi, et convinci coeperint ab eis qui nostrorum Librorum auctoritate non tenentur, ad defendendum id quod levissima temeritate et apertissima falsitate dixerunt, eosdem Libros sanctos, unde id probent, proferre conantur, vel etiam memoriter, quae ad testimonium valere arbitrantur, multa inde verba pronuntiant, non intellegentes neque quae loquuntur, neque de quibus affirmant."
St. Augustine, De Genesi ad litteram libri duodecim 1.19.39 (PL 34, col. 201), trans. John Hammond Taylor (ACW 41, pp. 42-43). Latin from this transcription of PL 34, not the critical edition.
"When I hear this or that brother Christian, who is ignorant of these matters and thinks one thing the case when another is correct, with patience I contemplate the man expressing his opinion. I do not see it is any obstacle to him if perhaps he is ignorant of the position and nature of a physical creature, provided that he does not believe something unworthy of you, Lord, the Creator of all things (1 Macc. 1:24). But it becomes an obstacle if he thinks his view of nature belongs to the very form of orthodox doctrine, and dares obstinately to affirm something he does not understand."
"cum enim audio christianum aliquem fratrem illum aut illum ista nescientem et aliud pro alio sentientem, patienter intueor opinantem hominem nec illi obesse video, cum de te, domine creator omnium, non credat indigna, si forte situs et habitus creaturae corporalis ignoret. obest autem, si hoc ad ipsam doctrinae pietatis formam pertinere arbitretur et pertinacius affirmare audeat quod ignorat."
St. Augustine, Confessions V.v/9, trans. Henry Chadwick. Cf. Thomas Aquinas, Reponsio de 43 articulis, prol.