Some disagreements are serious, others are footling. There are two disagreements about dreaming. They concern the questions ‘Do we wake or dream?’ and ‘Should we have confidence in dreams or in waking experience?’. The answer, said the Sceptics, is in each case: ‘Who knows?’. According to Galen, the sceptics aren’t serious, and no-one is genuinely puzzled by the questions — the disagreements are of the footling sort. That is true, and philosophically uninteresting. But the sceptical arguments which have exercised philosophers are, as Galen suggests, trifles; and in this case at least it is not difficult to let the fly out of the fly-bottle.