Therefore, since this servant of God has always been exalted, not only for the extraordinary facts of her life, but also for the rare virtues of her soul and the acumen of her spirit, we consider with certainty this fact a just and noble reason for which, as our predecessor Gregory XV decreed that she be honored as a saint so that all the faithful of Christ might understand with what abundance God had filled his servant with the Holy Spirit (cf Lett. Decr. Omnipotens sermo), We do not doubt having to proclaim her Doctor of the Church, the first among women, especially for her knowledge and doctrine of divine things. In fact, We have confidence and trust that Teresa of Jesus, who was declared by a solemn decree Teacher of Christian life, will also strongly stimulate the people of our time to grow in the love of contemplation in the soul and to the attainment of heavenly things.
Saint Paul VI
Multiformis Sapientia Dei (excerpt)
Apostolic Letter proclaiming St. Teresa of Avila a Doctor of the Church
27 September 1970