He was a genial companion, frank and outspoken, and a good man of business.
In Prague Jerome soon attracted attention by his advanced and outspoken opinions.
This having no effect, he issued the most outspoken of his works, De septem ecclesiae statibus, in which he reviewed the work of the reforming councils of his time, and, without touching the question of doctrine, championed a drastic reform of life and practice of the church on the lines laid down at Constance and Basel.
Here he distinguished himself by his outspoken criticism of the Austrian government, leading the opposition of the duchy to the exactions of the central power.
He was an ardent and outspoken supporter of Clay's compromise measures, and in 1850 he entered President Fillmore's cabinet as attorney-general, serving throughout the administration.