Not everyone tells the truth. ‘Read my lips: no new taxes.’ ‘This isn’t going to hurt.’ ‘I see no ships, my lord.’ ‘Of course I love you.’ When can we know what to believe? Four out of five of us don’t think politicians tell the truth, according to a recent MORI poll. But is telling the truth always the right or best thing to do? If it isn’t, what happens to trust? If it is, are there different kinds of truth? Do we always want to hear the truth? Do different professions need to have systemically different attitudes to truth-telling? Is there a moral difference between outright lies, falsehoods, deceits, dissimulation and just plain old ‘economy with the actualité’?