Cardinal Cathal Daly was described as having "a young head on old shoulders" when his latest book was launched in Veritas House, Dublin, yesterday.
Dr Patrick Masterson, formerly president of University College Dublin, and principal of the European University Institute in Florence, also said that the book, The Minding of Planet Earth, contained "youthful confidence and idealism".
He said the main theme of the book was expressed in the title.
"This has a double meaning. It refers, first of all, to God's mindfulness of the earth and then, correspondingly, to our responsibility to participate in that mindfulness.
"This is not just an elegantly written scholarly study. It is also a personal witness of joy in the Christian vocation to be mindful of the planet."
Cardinal Daly dedicated the book to the memory of the late Cardinal William Conway, who was archbishop of Armagh from 1963 to 1977. He noted that the cardinal kept in his study a photograph of planet Earth taken from the surface of the moon in July 1969 by the astronauts of Apollo XI, and the cover of the book was based on that photograph.