There are two elements in the spiritual life: first, a struggle against our lower nature; secondly, union of our wills with God, in other words, penance and love. St. Francis de Sales looks chiefly to love. Not that he neglects penance, which is necessary, but he wishes it to be practiced from a motive of love. He requires mortification of the senses, but he relies first on mortification of the mind, the will, and the heart. This interior mortification he requires to be unceasing and always accompanied by love. The end to be realized is a life of loving, simple, generous, and constant fidelity to the will of God, which is nothing else than our present duty. The model proposed is Christ, whom we must ever keep before our eyes. "You will study His countenance, and perform your actions as He did" (Intro., 2nd part, ch.1). The practical means of arriving at this perfection are remembrance of the presence of God, filial prayer, a right intention in all our actions, and frequent recourse to God by pious and confiding ejaculations and interior aspirations.
"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.
"Treatise on the Love of God", an authoritative work which reflects perfectly the mind and heart of Francis de Sales as a great genius and a great saint. It contains twelve books. The first four give us a history, or rather explain the theory, of Divine love, its birth in the soul, its growth, its perfection, and its decay and annihilation; the fifth book shows that this love is twofold - the love of complacency and the love of benevolence; the sixth and seventh treat of affective love, which is practiced in prayer; the eight and ninth deal with effective love, that is, conformity to the will of God, and submission to His good pleasure. The last three resume what has preceded and teach how to apply practically the lessons taught therein.