Geoffrey Dickens’s ancient dossier of (alleged) paedophiles in high places cannot be found among the 138 miles of government files, and rumour immediately takes wing. The ancients knew all about rumour: phêmê in Greek, fama in Latin, both words relating to ‘speech’.

In 415 bc, the Athenians sent an expedition to Sicily, and Syracuse was rife with rumours about it. In the Assembly, one speaker said it was all nonsense, stirred up by agitators wishing to create fear and thus gain power. It was a reasonable assumption: in 411 bc a revolution occurred in Athens as a result of rumour. Rumour has not lost its power as a modern political weapon either. Ancient grain-traders were also suspect: we hear of the charge that they spread rumours of storms and shipwreck designed to raise prices. Today’s stock markets are not exactly immune to the problem.

Greeks adopted two main criteria by which to evaluate such rumours. First, had the speaker himself been present at the event he was reporting, or had he just heard it from someone else? ‘Eyes are surer witnesses than ears,’ opined the philosopher Heraclitus; the Greek ‘know’ (oida) comes from same root as ‘see’ (eid-). It was common for a city to send its own men to witness for themselves what a messenger had reported.

Second, the credibility of the speakers: who knew them well enough to be able to vouchsafe for them, especially if they were messengers from outside the city-state? In particular, a man of high status was seen as more trustworthy than anyone of low status, especially if poor: that made him likely to lie for gain. So motive too had to be taken into account. It might be political or mercantile, as above, but it could be driven by a desire for a reward, or by treachery. Philip of Macedon said he could take any city by driving into it a donkey laden with gold.

What, then, can we say of the witness-value, credibility and motives of today’s rumour-mongers? Not to mention journalists?