What is a model? A model is like an Austrian timetable. Austrian trains are always late. A Prussian visitor asks the Austrian conductor why they bother to print timetables. The conductor replies "If we did not, how would we know how late the trains are?

In: H. Frauenfelder and E.M. Henley, Subatomic Physics, Part V (p. 351), Prentice-Hall, Inc., 1974