The Introduction to the Devout Life is one of the major works of literature.

It was during the year 1608 that the bishop of Geneva, Saint Francis de Sales (1567 - 1622), aged 41 and priest for 15 years, wrote this book. At the beginning, François de Sales wrote many advices to the wife of a cousin, Madame Louise du Chastel, who wanted to learn to be devout, and to know a life of prayer.

Now she had Francis de Sales' letters read around her, until a Jesuit asked her to publish them. Francis de Sales therefore agreed to take up the letters and publish them after some alterations, under the title Introduction to the Devout Life. The language and style used were simple for the time, with no Latin or Greek quotations. The book is intended for lay people and its main purpose is to show that it is possible to live a holy life while living in the world. The lives of saints, especially those who have lived in the world, are often taken as an example.

The book is divided into five parts: the first part teaches how to pass from the desire of the devout life to the resolution to embrace this life; the second part seeks to learn perfection through "prayer," that is, structured prayer, and the sacraments; the third part is devoted to the practice of virtues; the fourth part indicates the attitude to be towards temptations; and the last considers how to renew the fervor of the devotee.

This book was very quickly a huge success: it was thus reprinted more than forty times during the lifetime of François de Sales. The King of France Henry IV himself read it and Queen Marie de Medici offered a copy "adorned with diamonds" to the King of England.

Francis de Sales was proclaimed a saint and a doctor of the Church he is liturgically commemorated on January 24th.