the Marian teaching of Eligius, with whom Ildefonsus disagreed theologically. Ildefonsus utilises Isidore's "synonymous method" (or Synonyma Ciceronis) for theological purposes, wherein he repeats every phrase several times in different, although purportedly identical, ways. The identifications reveal the arguments in a rhetorically strong way, and lexicographers study the synonyms Ildefonsus used. Ildefonsus also probably wrote the Visigothic Mass of Ascension, which explains how the benefits received from Christ are richer than the wonders he performed, such as "ascending unaided to the clouds". Theologically, Ildefonsus regarded the Nicene Creed as sufficientem scientiam salutarem (sufficient knowledge for salvation) and as a foedus (compact) between believer and God. Like Isidore of Seville before him, Ildefonsus regarded the creed as forming "two pacts" between God and believer: one renouncing the devil, and another the statement of belief itself. Ildefonsus encouraged frequent Communion, implying that normal practice was infrequent, and insisted upon preparation, which may have discouraged many. Ildefonsus' De viris illustribus is a continuation, in thirteen parts, of a work of Isidore bearing the same name. The book contains no biblical quotations, but expands the biographies of famous writers to include illustrious leaders in the church and government, including Isidore himself (though Ildefonsus appears ignorant of Braulio of Zaragoza's better biography of Isidore). Ildefonsus' edition emphasised the monastic backgrounds of Toledo's earlier bishops (adding seven biographies). Nonetheless, modern editors note his pastoral concern and emphasis on praedicatio (preaching). Ildefonsus' continuation became an important historical source concerning Toledo during the 6th and 7th centuries. Ildefonsus also prepared an anthology of Isidore's works, excluding the Epistula ad Leudefredum. In his De cognitione baptismi, Ildefonsus explained the biblical origins of the sacrament, as well as Hispanic baptismal practices and important prayers. The work relied on Augustine's narrative concerning the psalms, as well as Gregory the Great's moral teachings, and Isidore's Etymologies. With respect to the latter, Ildefonsus dared to disagree with Isidore concerning Masses for the dead who had not had their last rites. Julian of Toledo in his Prognosticum followed Ildefonsus in arguing that such could still be effective. Ildefonsus also wrote De progressu spiritualis deserti elaborating on the same themes, analogizing baptism as a personal equivalent to the Israelites crossing the Red Sea, and the beginning of a personal spiritual journey. Several of Ildefonsus's letters to Quiricus of Barcelona survive. Julian of Toledo in the Elogium Ildefonsi mentions two lost works by Ildefonsus: Liber Prosopopoeia