To whom answerde Tiburce, "O suster deere,
Ne seydestow right now in this manere,
Ther nys but o God, lord in soothfastnesse?
And now of three how maystow bere witnesse?
– Geoffrey Chaucer
The Canterbury Tales, The Second Nun’s Tale. The doctrine of the Trinity, that there are three persons in one God, is one that many Christians admit that they don’t understand. So it is with Tiburtius, who is struggling with the idea when it is taught to him by Cecilia.