John, in spite of this tireless life, found time to work—both during the lifetime of his mentor, Bernardine, and afterwards—on the reform of the Order of Friars Minor. He also upheld, in his writings, speeches and sermons, theories of papal supremacy rather than the theological wranglings of councils (see Conciliar Movement). John, together with his teacher, Bernardine, his colleague, James of the Marche, and Albert Berdini of Sarteano, are considered the four great pillars of the Observant reform among the Friars Minor.