Above the entrance to the temple of Apollo in Delphi were a number of aphorisms. The first - nothing to excess - is relatively self-explanatory. The second - know thyself - was related to hubris and meant something along the lines of know your place. The third is more opaque to us now, but had something to do with being wary of making promises. Plutarch, the philosopher and one-time priest of the temple, speaks of a fourth: the letter E.

The original E - The E of the Sages - was cut from wood. After some victory or another the Athenians saw fit to replace it with one cast in bronze. That in turn was displaced by another in gold, courtesy of Lydia, wife to Augustus. All this in spite of the fact that the meaning of this E had been lost for centuries.

Plutarch discusses a number of possible interpretations in a dialogue. The E meant five and symbolised the five Wise Men. Or five the most important number in mathematics, physiology, philosophy and music. Or it referred to the alphabet's second vowel, and thus the second planet - the sun - and consequently pointed to Apollo. Or it meant the if that was asked of the oracle, or the if used in prayers, or the if in logic. Or - somehow - it suggested Apollo's immortality. Six protagonists. Seven hypotheses. They disagree. They argue. The dialogue ends, as was often the case, without resolution.

The E at Delphi was no longer a word or even a letter. It had instead become a space to think into, to muse upon. Seeded by a splinter from some long lost thought, seeded by an erasure, by a blur. We fill in the gaps. We join the dots. We trace the outline of our imaginations through the pinholes in the darkness above.