Lollardy, the English heresy that took its spring from the ideas of John Wyclif (c.1330–84), was defined by its books and their contents. The first condemnation of Wyclif himself, a bull sent out in 1377 by Pope Gregory XI, cited a list of nineteen errors quoted from his De civili dominio; these derived from the reading by the English Benedictine, Adam Easton, of a copy of book i which he had requested should be sent to him in Avignon. Already in 1382, the year in which the English ecclesiastical authorities finally censured twenty-four opinions deriving from Wyclif’s works (though not naming their author), a call was issued for the confiscation of written materials, and especially of bills issued by Wyclif’s Oxford disciples and disseminated through London and other parts of the country. From then on, and particularly after archbishop Arundel’s Constitutions of 1407, Lollards were often recognized from their books. An extreme case was that of John Claydon, a prominent London skinner, who, to judge by the long process against him, was burned at the stake in 1415 primarily because of his agreement with fourteen errors found in a copy of the Lanterne of Lizt which, notwithstanding his illiteracy, he had commissioned and had had read to him frequently. Claydon had been under suspicion before, but the story is illuminating: it shows not only how the authorities found written materials useful in their pursuit of heretics, but also the value set on books by the heretics themselves and one mode of their use.