When the confessors and learned men were Teresa’s own friars, their voice was familiar to her and it had the sound of her own traditions and of the doctrines and teachings of the Institutio. As men, they were inclined to approach and explain the reformed life and Carmelite spirituality in theological, scientific, and historical categories, bringing Carmel from isolation into dialogue with both the Church and the academy. Among them St. John of the Cross displayed a particular genius. According to his first biographer, José de Jesús Maria (Quiroga, 1562-1629) he had studied the spiritual heritage of Carmel in the light of patrology, history, and Bible in order to articulate the substance of contemplation, (Historia…del V. P. Fr. Juan de la Cruz, (Brussels 1628) 1.4.37-38)
John of the Cross was not the inventor of a new doctrine but a wise man who framed his doctrine in principles so diaphonous that their ultimate consequences are seen at a glance to follow from them. For St. John the supernatural life pivots on two hinges, the soul and God. God is like a seed infused in the depths of the soul where God dwells and whence God governs the soul and with it the whole body, so that God and the soul constitute in a sense one thing, thus making it possible to say with St. Paul “It is no longer I that live, but Christ lives in me” (Gal 2.20). The will is in charge of this supernatural metabolism. This transforming union takes place when the will submits itself completely to God’s will. And it is achieved by an absolute turning away from everything that does not come from God. Although this is spoken of as negation, it is positive in its significance, for it is made up of acts of the love of God. The Triune God is not an abstract concept but a spiritual reality implanted in the apex of the human spirit, which, in its turn, is surrounded by many corporal crusts, like a dwarf fan‑palm, to use the metaphor of St. Teresa (Interior Castle, I.2.8).
John of the Cross begins his elaboration of the doctrine of perfect union of the soul with God by analyzing the characteristics of the body and of the spirit or soul, whether intellectual or sensitive. Like many others in the sixteenth century, John drew his underlying philosophical concepts from the lineage of Neoplatonic thought that came down from antiquity through—among others—Clement of Alexandria, Augustine, the Victorines, and Bonaventure, to give modes of expression to Christian thought. The abstract concepts of Aristotelian thought, theologically represented by Thomism, could not adequately convey the clear exposition of the spiritual realities of which John wrote and which he intended to be not so much subjects of theological reflection as guides for the spiritual life. The first fruit of the doctrinal influence of St. John of the Cross appears in the Interior Castle of St. Teresa. She tells of the opportune intervention of a “learned man,” who was, in fact, John (Interior Castle. IV, 1.8). Teresa’s detailed analysis of the soul, pointing out potencies, passions, imaginations, thoughts, soul and spirit, is a superb treatise that shows the influence of John of the Cross (cfr. Efrén de la Madre de Dios, San Juan de la Cruz y el misterio de la Santísima Trinidad en la vida espiritual (Saragossa 1947).