In the next year Hall was chosen as one of the English deputies at the Synod of Dort. However he fell ill, and was replaced by Thomas Goad. At the time (1621–1622) when Marco Antonio de Dominis announced his intention to return to Rome, after a stay in England, Hall wrote to try to dissuade him, without success. In a long-unpublished reply (printed 1666) De Dominis justified himself in a comprehensive statement of his mission against schism and its limited results, hampered by Dort and a lack of freedom under James I.