Fr Ludwig Ott in “Fundamentals of Catholic Dogma” provides proofs from “Scripture” and “Tradition” that God “can be known with certainty, by the natural light of reason from created beings”:
Proof from Scripture:
According to the testimony of Sacred Scripture, the existence of God can be known:
a) From Nature: Wis. 13:1-9. Wis. 13:5: “For from the greatness and beauty of created things, their original author, by analogy, may be seen.” Rom 1:20: “For the invisible things of Him from the creation of the world are clearly seen, being understood by the things that are made. His eternal power and His divinity also: so that they are inexcusable.” The knowledge of God witnessed to in these two passages is a natural certain, immediate and easily achieved knowledge.
b) From Conscience: Rom. 2:14-15: “For when the Gentiles, who know not the (Mosaic) law do by nature these things that are of the law; these having not the law, are a law to themselves. They show that the works of the law are written in their hearts.” The pagans know naturally, without supernatural revelation, the essential content of the Old Testament law. In their hearts a law has been written whose binding power indicates a Supreme Lawgiver.
c) From History: Acts 14:14-16; 17:26-29. St. Paul, in his discourses at Lystra and at the Areopagus in Athens, shows that God reveals Himself in beneficent works also to the pagan peoples, and that it is easy to find Him, as He is near to each of us: “For in Him we live, and move and have our being” (Acts 17:28).
Proof from Tradition:
The Greek Fathers preferred the cosmological proofs of God which proceed from external experience; the Latin Fathers preferred the psychological proofs which proceed from inner experience. Cf. Theophilus of Antioch. Adv. Autol. I 4-5: “God has called everything into existence from nothing, so that His greatness might be known and understood through His works. Just as the soul in man is not seen, as it is invisible, but is known through the movement of the body, so God cannot be seen with human eyes; but He is observed and known through providence and His works. Just as one, at the sight of a well-equipped ship which sweeps over the sea and steers towards a harbour, becomes aware that there is a helmsman on her, who directs her, so also one must be aware that God is the director of everything, even though He is not seen with bodily eyes, as He cannot be apprehended by them.” Cf. St. Irenaeus, Adv. Haer. II 9,1; St John Chrysostom, In ep. ad Rom. hom. 3, 2 (on Rom. 1:19).
Fr Ott then asks the question whether humans can have an “innate idea of God?” He answers that the “Fathers teach that we must win [this] knowledge of God from contemplation of nature” and quotes St Thomas Aquinas to support his argument, In Boethium De Trinitate, q. 1a. 3 ad 6: “the knowledge of Him is said to be innate in us in so far as we can easily know the existence of God by means of principles which are innate in us.”
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