When, at the beginning of the year 1535, Blessed John Houghton, the Prior of the London Charterhouse, announced to his monks gathered together in Chapter that they must either renounce the authority of the Pope or suffer death, all cried with one mind and one voice: ‘Let us all die in our simplicity’. They had lived in simplicity, and it was in simphcity that they wished to die. But what exactly is this simplicity, which is the characteristic mark of every true Carthusian?