He had earned a master's in theology in 1972 under the supervision of Henri de Lubac, whose thought greatly shaped the Second Vatican Council.
After completing his studies in Lyon with de Lubac, Fr. Fessio asked for a suggestion of what to write this doctoral dissertation on, as well as under whom.
"De Lubac told me that one of the most important theologians of history, and maybe the most important theologian ever, was Hans Urs von Balthasar."
"And he added that the best person who could supervise a thesis on von Balthasar was the young professor Ratzinger in Regensburg, and he sent him a recommendation letter to receive me among his students."
The year Fr. Fessio completed his studies under de Lubac, the three professors – de Lubac, von Balthasar, and Ratzinger – founded the theological journal "Communio," which is now published in 14 international editions and stands for a renewal of theology in continuity with the living Christian tradition.
Under Ratzinger's supervision, Fr. Fessio wrote his dissertation "The Ecclesiology of Hans Urs von Balthasar" and graduated with a Ph.D. in 1976.
"Professor Ratzinger was exactly the way we learned to know him as Pope: simple, humble, clear in exposition, cultivated. One of the best professors I have ever met."
Discussing Benedict XVI's resignation this spring, Fr. Fessio said, "I was not surprised, since he spoke about this option with the journalist Peter Seewald, in the book 'Light of the World'."
Fr. Fessio maintained that the "decision to resign has been a decision of great 'modernity', and the Pope showed humility and courage in making it."
He added that "none of us in the circle could be in any way surprised by the modernity of Benedict XVI. I attended several meetings of the schuelerkreis, and every time Joseph Ratzinger had something new to say, something that no one had explored, or ever thought before."