What, indeed, is a head? For us, surely, it's as big as the world, as existence itself, and just as unknowable. It contains everything we are and everything we can ever know, including our own limits, because whatever we do we can never go beyond its bounds. The head is all, the centre of the universe, as well as in the long term its circumference. Small wonder, then, that heads have preoccupied artists from the very beginning of recorded time and still intrigue them, re-emerging, Hydra-like, as the central symbol of humanity.