Why did Tract 90 upset many members of the Church of England?

In 1841, St. John Henry Newman published Tract 90, which caused significant controversy within the Church of England because it attempted to reconcile the church's Thirty-nine Articles—a foundational Protestant document—with the teachings of the ancient, undivided church.1

Many members of the Church of England were upset because the tract appeared to argue that these articles were not incompatible with the doctrines of the Council of Trent, the formal Roman Catholic response to the Reformation. This interpretation suggested a shift toward Roman Catholic theology, which many Anglicans viewed as a betrayal of the church's Protestant identity. The alarm was further heightened when Newman’s disciple, W.G. Ward, explicitly claimed that the articles were indeed consistent with Roman Catholic doctrine. Consequently, the Bishop of Oxford requested the suspension of the Tracts for the Times, leading to widespread denunciations and Newman's eventual withdrawal from the movement's leadership.12