Teresa of Ávila has long been noted as one of the most influential Christian mystical teachers for her doctrine on contemplative prayer, mystical graces, and union with God. Her writings, especially the Life and The Interior Castle, have been widely read from the later sixteenth century to the present. Nevertheless, Teresa was far more than an enclosed contemplative totally separated from the world. Rather her biography reveals her as one of the most active and influential women of her time, especially because of her efforts to found seventeen houses of the reform of the Carmelite Order that she initiated in 1562. To understand how Teresa was able to combine contemplation and action it is necessary to investigate her main mystical writings in light of the major stages of her career as a reformer.