A retired theology professor from Germany and a post-doctoral student of Joseph Ratzinger at the University of Regensburg in the 1970s, Fr Horn said that the Pope Emeritus seemed frail but mentally "fresh" during an hour-long meeting to discuss the conference.
This will be the first time Benedict XVI will not attend the Schülerkreis, which is to meet at Castel Gandolfo from 29 August to 2 September.
Fr Horn said that Benedict XVI had nevertheless chosen the symposium's speaker and topic: "The question of God against the background of secularisation".