SIXTUS OF SIENA. - Biblical scholar, born in Siena in 1520 to Jewish parents, died in Genoa in 1569. As a young man, Sixtus converted and entered the Franciscans. Accused of heresy or relapse into Judaism, he was condemned to the stake; but, persuaded by Cardinal Ghisleri, he recanted and was pardoned by Julius III. He then entered the Dominicans and enjoyed the trust of St. Pius V (Ghisleri), who entrusted him with various tasks concerning the Inquisition. In particular, Sixtus carried out his activity in Cremona, overseeing Hebrew publications. There he saved not a few manuscripts and books in that language.
Sixtus wrote a *Bibliotheca sancta* (Venice 1566) in eight books, which is a critical examination of the sacred Scriptures, with refutations of objections raised against them (Books VII-VIII). In this work, he first introduced the division of biblical books into "protocanonical" and "deuterocanonical" (and "apocryphal").
Sixtus mentions various other writings of his that have not come down to us: a book *De usu concordantiarum S. Bibliae*, four books on biblical texts of an astronomical, geographical, or scientific nature (*Astronomicarum, geographiarum, physicarum quaestionum*) or more controversial ones (*In varios Divinae Scripturae locos problematicarum epistolarum liber*), a concordance or harmony of the four sapiential books (*Proverbs, Ecclesiastes, Wisdom, and Sirach*), commentaries on the *Epistle to the Romans* and on various Gospel passages, as well as on the first chapters of *Genesis* and *Job*, and on *Psalms 1 and 51* (cf. *Bibliotheca sancta* [V. BIBLICA.], pp. 475).