Here, too, he published, in 1531, his most important work, the Chronica, Zeitbuch and Geschichtsbibel, largely a compilation on the basis of the Nuremberg Chronicle (1493), and in its treatment of social and religious questions connected with the Reformation, exhibiting a strong sympathy with heretics, and an unexampled fairness to all kinds of freedom in opinion.
In matters of doctrine the pope supported Bernard of Clairvaux in his prosecution of Abelard and Arnold of Brescia, whom he condemned as heretics.
His apologists explain that his action was merely "official," but Bonner was one of those who brought it to pass that the condemnation of heretics to the fire should be part of his ordinary official duties.
The enforcement of the first Book of Common Prayer had also been part of his official duties; and the fact that Bonner made no such protest against the burning of heretics as he had done in the former case shows that he found it the more congenial duty.
Among the principal events of that reign must be reckoned the foundation of the two orders, Franciscan and Dominican, who were destined to form a militia for the holy see in conflict with the empire and the heretics of Lombardy.