Saint Teresa, began to write the Interior Castle on June 2, 1577, Trinity Sunday, and completed it on the eve of St. Andrew, November 29, of the same year. But there was a long interruption of five months, so that the actual time spent in the composition of this work was reduced to about four weeks-a fortnight for the first, and another fortnight for the second half of the book. The rapidity with which it was written is easily explained by the fact that the Saint had conceived its plan some time previously. On January 17, 1577, she had written to her brother, Don Lorenzo de Cepeda, at Avila: 'I have asked the bishop-Don Alvaro Mendoza-for my book (the Life) because I shall perhaps complete it by adding those new favours our Lord has lately granted me. With these one may even compose a new work of considerable size, provided God grants me the grace of explaining myself."-From the Introduction.