In this famous Treatise, St Peter of Alcantara assists the Catholic soul to find devotion, that supernatural affection that removes distaste for spiritual effort and urges one on to serve God joyfully and generously. St Peter made this book short and simple, yet packed into it "all that is necessary to know about prayer." It is full of saintly counsels on prayer, which is the key to the entire spiritual life. The reader of the Treatise will access the classic Catholic wisdom on mental prayer, including what to think about, how to follow a method, when to disregard a method, the importance of the heart over the head, what to do in times of spiritual dryness and much more. This introduces souls to mental prayer as a means of obtaining all spiritual goods. St Peter of Alcantara was a 16th-century Spaniard and a spiritual director of St Teresa of Avila, the great Doctor of Prayer. He was known for his severe penances and after he died, he is said to have appeared to St Teresa and exclaimed: "O blessed penance that has led me to Heaven!"