What does the Church mean when she recognizes private revelations and visions as credible? Which is the point at which God affects the soul? What are the criteria for the discernment of genuine prophecies. Kari Rahner's concern is the theological and psychological significance of phenomena which, despite the Church's care in establishing their authentic character, have been left too often and too readily to human credulity. The danger of error, he suggests, is greater in credulity than in scepticism. He offers what is in effect a general theory that "genuine" private revelations are to be judged as an overflow into the sensibility of a primarily spiritual impulse and, consequently, combine "subjective" with "objective" elements. Mystical visions deserve the respect due t.r the spiritual life of sane and devout people, but the supernatural agency is not to be presupposed but must be proved. As regards prophetic visions, their only absolute criterion is a miracle performed in connection with the prophecy so as to be understood as its confirmation. Expressing reservations on the alleged miracles of Fatima and La Salette Father Rahner shows that divine prophecies cannot be intended to restrict human liberty and, in Post-apostolic times, must fit into the framework of scriptural prophecy. This is a bold application of theological principles to a subject beset by devotional prejudices and preconceptions.