The Roman inquisition became a force in Modena during the papacy of Pope Paul IV, who opposed the softer policy exercised by Bishop Foscarari and his patron, Cardinal Giovanni Morone.

[3] Already in 1542 Castelvetro, with the rest of the Academy of Modena, had been obliged to sign a formulary protesting orthodoxy in matters of faith.

Together with his brother Giovanni Maria, who thus suffered for aiding his escape, Castelvetro was condemned and excommunicated as a hardened heretic (1561).

[4] His Giunta, a commentary on the Prose della volgar lingua by Pietro Bembo, is one of the earlier texts on Italian grammar, and linguistics in general; his contemporaries objected to him that his theories were a little too philosophical for their time.

After Castelvetro's Poetics (Vienna, 1570) his best-known work is a commentary on the Italian poems of Petrarch: Le Rime del Petrarca brevemente sposte, Basel, 1582.