His “Disputations on controversies of the Christian Faith” against heretics constitute “clearly the most noble” and arduous work.

This, the greatest of Bellarmine's works deftly refuted the new attacks which the Magdeburgians had but recently carried out with their “Centuries” as they say, by means of which, especially by employing speciously historical arguments and the testimonies of the Fathers and the ancients, they had attempted to destroy the Roman Church.

No wonder therefore that as soon as Bellarmine's “Disputations on controversies of the Christian faith” were read in the City [i.e. Rome], in the Gregorian University, they abundantly surpassed all expectations of them that they had aroused: that they were printed and published again and again, being desired and sought after continually by everyone; that their author was regarded by very many Catholic theologians not only in his own times, but even in our own, as the Master of Controversies.

But it is an outstanding achievement of St Robert, that the rights and privileges divinely bestowed upon the Supreme Pontiff, and those also which were not yet recognised by all the children of the Church at that time, such as the infallible magisterium of the Pontiff speaking ex cathedra, he both invincibly proved and most learnedly defended against his adversaries. Moreover he appeared even up to our times as a defender of the Roman Pontiff of such authority that the Fathers of the [1870] Vatican Council employed his writings and opinions to the greatest possible extent. Nor to be passed over in silence are his sacred sermons and catechetical works, especially the famous Catechism “which has been approved by its use throughout the ages and by the judgement of very many of the Church's bishops and doctors”.

As a lamp placed on a candlestick to give light to all that are in the house, he illuminated by word and deed Catholics and those straying from the unity of the Church; as a star in the firmament of the sky he laid bare the truth which he promoted above all else to all men of good will “by the magnificent rays of his knowledge, rays as wide as they were high, by the splendour of his outstanding and brilliant genius”; the first apologist not only of his own age but of subsequent ages as well, by the strenuous defence of the Catholic dogmas that he took upon himself he commended himself to the memory and admiration of all those who follow the Church of Christ with genuine love.