Jewish story told by Martin Buber (taken from Ratzinger’s Introduction to Christianity):

An adherent of the Enlightenment, a very learned man, who had heard of the Rabbi of Berditchev, paid a visit to him in order to argue, as was his custom, with him, too, and to shatter his old-fashioned proofs of the truth of his faith. When he entered the Rabbi’s room, he found him walking up and down with a book in his hand, rapt in thought. The Rabbi paid no attention to the new arrival. Suddenly he stopped, looked at him fleetingly, and said, “But perhaps it is true after all.” The scholar tried in vain to collect himself - his knees trembled, so terrible was the Rabbi to behold and so terrible his simple utterance to hear. But Rabbi Levi Yitschak now turned to face him and spoke quite calmly: “My son, the great scholars of the Torah with whom you have argued wasted their words on you; as you departed you laughed at them. They were unable to lay God and his Kingdom on the table before you, and neither can I. But think, my son, perhaps it is true.” The exponent of the Enlightenment opposed him with all his strength; but this terrible “perhaps” that echoed back at him time after time broke his resistance.