What is time? as long as no one asks me, I know what it is; but if I wish to explain it to an enquirer, then I do not know.
St. Augustine, Confessions, bk. XIV, xvii. Trans. E. B. Pusey, ed. T. Scott (London, 1921) 262.

時間究竟是什麼？沒有人問我，我倒清楚，有人問我，我想說明，便茫然不解。
奧古斯丁，《懺悔錄》，卷十一，第十四章。