John of the Cross is known especially for his writings. He was mentored by and corresponded with the older Carmelite, Teresa of Ávila. Both his poetry and his studies on the development of the soul are considered the summit of mystical Spanish literature and among the greatest works of all Spanish literature. He was canonized by Pope Benedict XIII in 1726. In 1926 he was declared a Doctor of the Church by Pope Pius XI, and is commonly known as the "Mystical Doctor".