I shall start with a joke and go on with a riddle. The joke first: in Woody Allen's film Take the Money and Run young Virgil, a future criminal, who is clumsy and unlucky, suddenly comes into view, in the middle of the school band, going along the streets of the town playing the cello; in this brief episode the mismatch between the instrument and the situation is complete, absolute, since the cellist could obviously not follow the rhythm of the procession. The riddle next: why do policemen always go around in pairs? Because one can read and the other can write. So the two skills complement each other unreliably, whereas they ought to exist together in the same person.