A condemnatory term for the adaptation of church doctrine and practice to American culture which provoked controversy (and condemnation by Pope Leo XIII) within the Roman Catholic Church in the late nineteenth century. The trouble originated in conflict between progressives and traditionalists in the American Church over the value of parochial schools, and whether it was wise to try to preserve the native language and culture of immigrants in order to protect their faith, or rather to help them adopt American customs. When the biography of an American progressive priest, I.T. Hecker,* by W. Elliott was translated into French, conservative French priests denounced the ideas contained in it as “Americanism.” American progressive bishops such as James Gibbons* were accused of subverting the Faith. In his apostolic letter of 1899 addressed to Gibbons, Leo condemned such errors as the rejection of religious vows, the assertion that external religious authority is unnecessary in a time of liberty, and the view that natural and active virtues are more valuable in the modern world than are supernatural and passive. Gibbons denied that such views were held by American Catholics.