Teresa of Ávila was the 16th-century Spanish mystic and Doctor of the Church who reformed the Carmelite order and wrote The Interior Castle.
Born Teresa Sánchez de Cepeda y Ahumada in 1515, she entered the Carmelite convent at Ávila. Concerned that convent life had become too relaxed and socially distracted, she promoted a stricter observance centred on prayer, contemplation, poverty, and enclosure. Her reform produced the Discalced Carmelites, meaning “barefoot Carmelites.”
Teresa founded numerous convents across Spain and worked with John of the Cross, who helped establish the reformed male branch. Her reform faced strong opposition, including restrictions imposed by unreformed Carmelites, but royal and papal support eventually allowed it to continue.
The Interior Castle, written in 1577 and published in 1588, presents the soul as a crystal castle containing seven mansions. The work describes spiritual growth toward union with God. Teresa is sometimes confused with Catherine of Siena or Thérèse of Lisieux, but she was the Spanish Carmelite reformer and the author of this particular book. She was named a Doctor of the Church in 1970.