317-319, he asks: An Moyses potuerit scribere prophetice in verbis suis ista quae habentur hic vel scripserit literam istam Esdras et Josue (Could Moses have written these things prophetically in his own words?

[4] He is also known as an early theorist on witchcraft; in his De maleficis mulieribus, quae vulgariter dicuntur bruxas (1440) he defended the possibility of flying witches based on biblical exegesis.

By great application joined to an unusually brilliant mind and an extraordinarily retentive memory, he accumulated such a vast store of knowledge that his contemporaries styled him a wonder of the world.

During a visit to the papal court at Siena in 1443, he was denounced to Pope Eugene IV as having publicly defended a heretic and some rash propositions, but in an explanatory letter he assured the pontiff of his orthodoxy.

On his return to Spain, he entered briefly the Carthusian monastery of Scala Dei in January 1444 but was appointed Grand Chancellor and councillor of John II of Castile just three months later and moved to the court.