Wyclif devoted many years of his life to the intensive study of scripture, beginning formally with exegetical lectures that survive as a sequence of postils (probably written between 1371 and 1376), now collectively known as Postils on the Whole of the Bible, a unique and extensive commentary that won Wyclif considerable respect as an exegete. In these, we witness his meticulous defence of the authority of scripture, and of the literal veracity of all of its parts. This is developed further in On the Truth of Holy Scripture (1377–78), Wyclif’s definitive guide to the interpretation of the Bible. It is in the first book of this latter treatise that he argues that scripture is metaphysically the Book of Life of which we read in St John’s Apocalypse. This book and the truths inscribed within it, he suggests here, are scripture in the truest sense, unlike the material codices that are so often taken to be the scriptural text by contemporary scholars. This conception of the scripture served Wyclif well in his famous claim that no part of scripture could literally be false. It enabled him to challenge the linguistic sophistry which he felt inevitably arose when the nature of the scriptural text was narrowly equated with inscriptions on manuscript pages.