Roberto Bellarmino was born in Montepulciano in 1542, and at the age of 18 entered the Jesuit Order. After teaching in Florence and Mondovi, he moved to Belgium, where he was ordained a priest in 1570. He returned to Rome in 1576 and became a professor of theological controversies at the Roman College. Bellarmino was a theologian of great fame and prestige, and involved himself in the disputes which grew up around Galileo's discoveries. In 1611 he asked the professors of mathematics at the Roman College to express their opinions on the issues raised by the telescope, concerning the surface of the moon, the phases of Venus, the satellites of Jupiter, the shape of Saturn, and the composition of the Milky Way. The answer he received from Clavius (1538-1612) and his pupils was favorable to Galileo, but in spite of these apparent triumphs something at Rome was working against him. In that same year of 1611, on May 17, during a meeting of the Holy Office at which Bellarmino was present, a deliberation was made to examine whether at the trial of Cesare Cremonini (1550-1631), a philosopher at the University of Padua, mention had also been made of Galileo, who had been a friend and colleague of his. Several years prior to this Bellarmino had also participated in the last phase of the trial of Giordano Bruno (1548-1600), as he had in the affair of the interdiction of the Venetian Republic.

Some years later, in 1615, Bellarmino took a prominent role in the procedure which led to the suspension of Copernicus' (1473-1543) D e revolutionibus (Nuremberg, 1543) and the warning issued to Galileo. The year before, in 1615, in a letter to Antonio Foscarini (1580-1616) author of a Lettera... sopra l' opinione de' Pittagorici e del Copernico della mobilità della terra e stabilità del sole e del nuovo pittagorico sistema del mondo [Letter concerning the opinion of the Pythagoreans and Copernicus about the motion of the earth and the fixity of the sun and about the new Pythagorean world system], Bellarmino had steadfastly maintained that Copernicanism could only be considered as a mere mathematical hypothesis. Also, any attempt to interpret holy scripture that ignored the commentaries of the Fathers smacked of practices of the reformed churches and violated the Council of Trent.

Bellarmino died in Rome in 1621. In 1930 Pope Pius XI (1857-1939) beatified Roberto Bellarmino as a saint and doctor of the Church.