Bullinger moved to the university of Cologne July 8, 1519, at the college Bursæ-Montis. There the works of the school-divines, and chiefly of Peter Lombard and Gratian, soon engrossed his attention; and, in the providence of God, were converted into instruments for detaching him from the religion of Rome. For in this course of reading meeting with frequent extracts from the fathers, he felt an earnest desire quickened within him to peruse their entire writings. Accordingly, he solicited and obtained admission to a well-stored library of the Dominicans; and there studied with intense ardour several treatises of Chrysostom, Ambrose, Origen, and Augustine.
Simultaneously [while at Cologne in 1520-21] the earlier tracts of Luther, especially his “Babylonish Captivity” and treatise “On Christian Liberty,” with the “Loci Communes” of Melancthon, came into his hands. He procured for himself also a copy of the New Testament [in Greek], and devoted days and nights to the perusal of it, with the aid of the Commentaries of Jerome. The result of these pursuits was, that Bullinger’s mind and heart opened gradually to the knowledge and reception of the gospel in its purity.*
*Harding’s introduction to the English translation of The Decades of Bullinger.