A runaway slave, in the Greek world, might take refuge in the house of someone whom he had met at his master's and beg his new protector not to send him back. If he made a good impression, he might be a cause of some embarrassment to his protector, who would either have to keep the slave against the wishes of his former master or send him back to certain punishment; and if the two men were friends this might be a genuinely difficult decision. We happen to possess two letters of the Latin writer Pliny which are concerned with precisely this dilemma. Pliny solved it by sending back the culprit with a carefully worded letter in which he asked his friend to receive the slave kindly. This letter of Paul appears to be of exactly the same kind.

The culprit in question was certainly a slave. But what exactly had he done? It has traditionally been assumed that he had run away from his master Philemon and taken refuge with Paul, who had converted him to Christianity; but the only evidence for this is the sentence in which Paul says that he was formerly useless to Philemon – and he evidently chose this word, not because it described exactly how Onesimus had behaved, but because it was a pun on his name (onēsimus, ‘useful’).