"An Introduction to the Devout Life," a work intended to lead "Philothea," the soul living in the world, into the paths of devotion, that is to say, of true and solid piety. Every one should strive to become pious, and "it is an error, it is even a heresy," to hold that piety is incompatible with any state of life. In the first part the author helps the soul to free itself from all inclination to, or affection for, sin; in the second, he teaches it how to be united to God by prayer and the sacraments; in the third, he exercises it in the practice of virtue; in the fourth, he strengthens it against temptation; in the fifth, he teaches it how to form its resolutions and to persevere. The "Introduction," which is a masterpiece of psychology, practical morality, and common sense, was translated into nearly every language even in the lifetime of the author, and it has since gone through innumerable editions.