From the Roman Martyrology: At Rome, the birthday of St. Robert Bellarmine of the Society of Jesus, confessor and cardinal, and also formerly bishop of Capua. He is noted for his holiness, learning, and the many great tasks he performed in defence of the Catholic faith and the Apostolic See. Pope Pius XI bestowed on him the honours of the saints, declared him to be a doctor of the universal Church, and appointed the 13th of May as his feast day.
From the Doctors of the Church:
St Bellarmine was a traditionalist and yet acted and lived untraditionally when it came to ministering to others and extending himself far beyond the norm. The love of God penetrated him profoundly. His heart was with the poor and broken, yet, he was unafraid to live with the powerful and had an apartment at the Vatican. However, living there did not prevent him from relaxing any of his former austerities. This was in addition to his poor health that plagued him all his life. It was perhaps his heaviest cross.
Our Jesuit scholar knew Scripture thoroughly. He believed that living out the Good News was more than knowing it. Robert knew that the source of divine revelation was a "living" Christ. The content of faith is one matter but the source is what defines the content. It was vital to our saint to get across the meaning of being a Christian. His aim was to be a good example and pass along the love of God. In this manner he would imitate Jesus and show His virtues. That for him was very important and necessary to be a Christian. He was humble and never allowed himself to become too attached to anything passionately. To love God ardently in all things, and remain detached, is an art which only the Artisan of souls, the Holy Spirit, can lead and direct.
For this Doctor, detachment from others is best made by attachment to the people and things of God. He always had the service of the Church foremost in mind. The more he stepped down the more God raised him up with honor and responsibilities. One becomes responsible not by give up things which the word detachment means but by taking on more things and becoming more responsible.
The Pope made him a cardinal and insisted on having him by his side as his personal theologian. He was head of the Vatican Library, a member of nearly every congregation and played an important role in the affairs of the Holy See.
Robert developed the theory of the indirect power of the pope in temporal affairs. This was a very big first step that had not happened in the history of the Popes. Popes wield temporal and spiritual powers. St Bellarmine wanted popes to focus primarily on the spiritual powers than the temporal affairs.
He played a significant role working with the laity. His catechisms, his writings, his example with children, young adults and older Christian all reveal his Christ-like works and actions.
He all but eliminated the divine-rights-of-kings untenable principle that had been in existence many years. "Disputations on the Controversy" is his most famous book which highlights the power issue. His explanation on this issue was crystal-clear and became the benchmark in textbooks for centuries.
The Fifteen Marks of the Catholic Church by St. Robert Bellarmine