The account of her spiritual life contained in the "Life written by herself" (completed in 1565, an earlier version being lost), in the "Relations", and in the "Interior Castle", forms one of the most remarkable spiritual biographies with which only the "Confessions of St. Augustine" can bear comparison. To this period belong also such extraordinary manifestations as the piercing or transverberation of her heart, the spiritual espousals, and the mystical marriage. A vision of the place destined for her in hell in case she should have been unfaithful to grace, determined her to seek a more perfect life. After many troubles and much opposition St. Teresa founded the convent of Discalced Carmelite Nuns of the Primitive Rule of St. Joseph at Avila (24 Aug., 1562), and after six months obtained permission to take up her residence there. Four years later she received the visit of the General of the Carmelites, John-Baptist Rubeo (Rossi), who not only approved of what she had done but granted leave for the foundation of other convents of friars as well as nuns. In rapid succession she established her nuns at Medina del Campo (1567), Malagon and Valladolid (1568), Toledo and Pastrana (1569), Salamanca (1570), Alba de Tormes (1571), Segovia (1574), Veas and Seville (1575), and Caravaca (1576). In the "Book of Foundations" she tells the story of these convents, nearly all of which were established in spite of violent opposition but with manifest assistance from above. Everywhere she found souls generous enough to embrace the austerities of the primitive rule of Carmel. Having made the acquaintance of Antonio de Heredia, prior of Medina, and St. John of the Cross (q.v.), she established her reform among the friars (28 Nov., 1568), the first convents being those of Duruelo (1568), Pastrana (1569), Mancera, and Alcalá de Henares (1570).
A new epoch began with the entrance into religion of Jerome Gratian, inasmuch as this remarkable man was almost immediately entrusted by the nuncio with the authority of visitor Apostolic of the Carmelite friars and nuns of the old observance in Andalusia, and as such considered himself entitled to overrule the various restrictions insisted upon by the general and the general chapter. On the death of the nuncio and the arrival of his successor a fearful storm burst over St. Teresa and her work, lasting four years and threatening to annihilate the nascent reform. The incidents of this persecution are best described in her letters. The storm at length passed, and the province of Discalced Carmelites, with the support of Philip II, was approved and canonically established on 22 June, 1580. St. Teresa, old and broken in health, made further foundations at Villnuava de la Jara and Palencia (1580), Soria (1581), Granada (through her assiatant the Venerable Anne of Jesus), and at Burgos (1582). She left this latter place at the end of July, and, stopping at Palencia, Valldolid, and Medina del Campo, reached Alba de Torres in September, suffering intensely. Soon she took to her bed and passed away on 4 Oct., 1582, the following day, owing to the reform of the calendar, being reckoned as 15 October. After some years her body was transferred to Avila, but later on reconveyed to Alba, where it is still preserved incorrupt. Her heart, too, showing the marks of the Transverberation, is exposed there to the veneration of the faithful. She was beatified in 1614, and canonized in 1622 by Gregory XV, the feast being fixed on 15 October.
St. Teresa's position among writers on mystical theology is unique. In all her writings on this subject she deals with her personal experiences, which a deep insight and analytical gifts enabled her to explain clearly. The Thomistic substratum may be traced to the influence of her confessors and directors, many of whom belonged to the Dominican Order. She herself had no pretension to found a school in the accepted sense of the term, and there is no vestige in her writings of any influence of the Aeropagite, the Patristic, or the Scholastic Mystical schools, as represented among others, by the German Dominican Mystics. She is intensely personal, her system going exactly as far as her experiences, but not a step further.
A word must be added on the orthography of her name. It has of late become the fashion to write her name Teresa or Teresia, without "h", not only in Spanish and Italian, where the "h" could have no place, but also in French, German, and Latin, which ought to preserve the etymological spelling. As it is derived from a Greek name, Tharasia, the saintly wife of St. Paulinus of Nola, it should be written Theresia in German and Latin, and Thérčse in French.
1 -[Saint Teresa of Avila]
2 -[Saint Teresa of Avila : Works]
Source : BENEDICT ZIMMERMAN, Transcribed by Marie Jutras in http://www.newadvent.org/