Benedictine monk Benedetto Fontanini wrote the first version of the most notable expression of Spirituali doctrine, the Beneficio di Cristo (The Benefit of Christ's Death), in 1543, attempting to prove that salvation comes through Sola fide, or 'faith [in Christ] alone' (as Protestants insisted on), not through works or the Church; later the poet and humanist Marcantonio Flaminio revised it.
The group printed forty thousand copies of the book, which was soon declared heretical and placed on the Index Librorum Prohibitorum.
Although Spirituali occupied positions of high power within the ecclesiastical hierarchy, and may have even held the sympathy of Pope Paul III, they failed to achieve much change, and more conservative "fundamentalist" zelanti currents set the Church on a course of confrontation with the Protestants at the Council of Trent (1545–1563), lumping them in with them.
The Spirituali's lack of success stemmed from inadequate support by the Church hierarchy, and the movement was doomed when Cardinal Pole, who was the choice of Pope Paul III, lost the papal election in 1549–1550 by one vote, after which their position made them suspect to both Protestants and conservative Catholics, allowing them to be outmaneuvered and defeated.
Cardinal Pole fled to England, while Paul IV tried unsuccessfully to have him brought back before the Catholic Inquisition.