 He (and Mirabeau) promoted the appropriation of Church properties.He participated in the writing of the Declaration of the Rights of Man and proposed the Civil Constitution of the Clergy that nationalised the Church, and swore in the first four constitutional bishops, even though he had himself resigned as Bishop following his excommunication by Pope Pius VI in 1791.During the "Fête de la Fédération" on 14 July 1790, Talleyrand celebrated Mass.