[Reposted from Scriptural Postscript.]
Many learned Christians offer rational proofs of God’s existence and attributes to the incredulous who seek such proof. St. Thomas Aquinas offered five superbly logical proofs in his Summa Theologica (I, 2, 3). Even Aristotle, centuries before, offered similar proofs.
But knowledge obviates faith inasmuch as one cannot know a thing with certainty and believe in it in the same respect. Belief necessarily involves some degree of objective uncertainty. The believer believes in divine truths as if he possesses scientific certainty of them, though he actually does not possess such certainty. His faith affords him subjective certainty where objective certainty is lacking.
Christ would have us value faith above certainty. He said: “Blessed are they who believe without seeing” (Jn 20:29). And St. Paul taught that we are saved by grace through faith (Eph 2:8).
The sort of faith that enables one to attain everlasting life is supernatural faith, a gift from God enabling a person to assent to divine truths with his will. It is not a human faith, the kind we use daily when we accept the word of others and build upon the scientific knowledge of those who have gone before us.
Should an unbeliever’s doubt be replaced by nothing more than rationally demonstrable certainty, his new-found confidence would not enable him to reach Heaven. But should his doubt be replaced by a willful assent to all that God’s duly-appointed teachers have proposed to him as necessary to believe concerning matters of faith and morals, even though he does not adequately understand these things by human reasoning alone, then he would be well on his way to his proper end in God. Rational proofs may signal the start of a journey, but faith carries one through to a clear knowledge of God and everlasting life in Him.