R. Johanan was sitting and teaching: The Holy One, blessed be He, will bring jewels and precious stones, each thirty cubits long, and thirty cubits high, and make an engraving in them, ten by twenty cubits, and set them up as the gates of Jerusalem, for it is written, And I will make thy windows of agates, and thy gates of carbuncles. A certain disciple derided him saying, 'We do not find a jewel even as large as a dove's egg, yet such huge ones are to exist!' Some time later he took a sea journey and saw the ministering angels cutting precious stones and pearls. He said unto them: 'For what are these?' They replied: 'The Holy One, blessed be He, will set them up as the gates of Jerusalem.' On his return, he found R. Johanan sitting and teaching. He said to him: 'Expound, O Master, and it is indeed fitting for you to expound, for even as you did say, so did I myself see.' 'Wretch!' he exclaimed, 'had you not seen, you would not have believed! You deride the words of the Sages!' He set his eyes upon him, and he turned in to a heap of bones.
Sanhedrin 100a, Soncino translation
Many persons are very sensitive of the difficulties of religion; I am as sensitive as any one; but I have never been able to see a connection between apprehending those difficulties, however keenly, and multiplying them to any extent, and doubting the doctrines to which they are attached. Ten thousand difficulties do not make one doubt, as I understand the subject; difficulty and doubt are incommensurate. There of course may be difficulties in the evidence; but I am speaking of difficulties intrinsic to the doctrines, or to their compatibility with each other. A man may be annoyed that he cannot work out a mathematical problem, of which the answer is or is not given to him, without doubting that it admits of an answer, or that a particular answer is the true one.
John Henry Newman, Apologia Pro Vita Sua, Part VII