This controversial literature, cultivated on a large scale, was designed to defend Judaism against calumny and abuse, rather than to convert a single Christian soul. Its aim was to open the eyes of Jews, so that ignorance or credulity might not lead them into the snares prepared for them. Doubtless it also desired to stir up the new-Christians, and to re-animate their Jewish spirit beneath the disguise they had assumed to save their lives. Hence the majority of the polemical writings of the day were merely vindications of Judaism from the old charges fulminated by Nicholas de Lyra a century before, or more recently by Geronimo de Santa Fé and others, and widely circulated by the Christian clergy. Solomon-Paul of Burgos, who had been appointed bishop of his native town, wrote, in his eighty-second year (1434, a year before his death), a venomous tract against Judaism --"Searching the Scriptures" (Scrutinium Scriptuarum)--in the form of a dialogue between a teacher and his pupil, the unbelieving Saul and the converted Paul. Solomon-Paul does not seem to have retained much of the wit which, according to Jewish and Christian panegyrists, had at one time distinguished him--it had probably become blunted amid the luxurious ease of the episcopal palace--for his tract, devoutly Christian and Catholic in tone, is pointless and dull. Another ex-rabbi who devoted himself to attacking Judaism was Juan de España, also called Juan the Old (at Toledo), a convert who in old age had embraced Christianity under the influence of Vincent Ferrer's proselytizing efforts. He wrote a treatise on his own conversion and a Christian commentary on the seventy-second Psalm, in both of which he asserted the genuineness of his change of creed, and urged the Jews to abjure their errors. How many weak-minded Jews must have been influenced by the zeal, earnest or hypocritical, of such men as these, belonging to their own race, and learned in their literature!