The test of a round character is whether it is capable of surprising in a convincing way. If it never surprises it is flat. Flat characters ... in their purest form ... are constructed round a single idea or quality; when there is more than one factor to them, we get the beginning of the curve toward the round. The really flat character can be expressed in one sentence such as, "I will never desert Mr. Micawber." There is Mrs. Micawber — she says she won’t desert Mr. Micawber; she doesn’t, and there she is.

E.M. FORSTER