A Doubting Thomas is someone who will refuse to believe something without direct, physical, personal evidence; in other words, a skeptic.
Famous quotes containing the words doubting and/or thomas:
“It would strike me as ridiculous to want to doubt the existence of Napoleon; but if someone doubted the existence of the earth 150 years ago, perhaps I should be more willing to listen, for now he is doubting our whole system of evidence.”
—Ludwig Wittgenstein (1889–1951)
“The vain travail hath wearied me so sore,”
—Sir Thomas Wyatt (1503?–1542)