The author of the article on Mysticism in the Dictionnaire de Thèologie Catholique bases his study on the idea of the experimental knowledge of God. It is an idea that anyone wanting to treat the problem by the inductive and psychological method would be bound to arrive at. The theologian tries to confine this field of enquiry within concepts and laws, and he will define mysticism as the predominant influence of the gifts of the Holy Ghost in a Christian life. This is the standpoint we must take up if we want to discover St Thomas's attitude, and in the end our problem will amount to this: what place have the theology and the activity of the gifts of the Holy Ghost in the organism of the life of grace? Both, in fact, depend on those attributes that enrich and transform human nature, attributes called, in a word, the supernatural life.