The Spirit of Catholicism is a work of high theology written for a lay audience, eschewing technical terms for lucid and often beautifully poetic language. It is widely acknowledged to be one of the best introductions to Catholic Christianity available today; even George Orwell, non-believing but fair-minded (unlike many prominent Englishmen nowadays, alas), praised it in his own snarky way. Thus, it comes highly recommended by leading lay evangelists like Scott Hahn, a convert from Protestantism, and Dave Armstrong, who describes it as “perhaps the best book written about the Catholic Church in the 20th century. Must reading for Catholic and non-Catholic alike”.
In The Spirit of Catholicism, Karl Adam presents a panoramic view of the Catholic Faith from the perspective of the Incarnation, the revelation that God the Son became man in Jesus Christ for humanity’s salvation. The Incarnation shows that, even as salvation is entirely a Divine act, it is carried out through human freedom and cooperation: God the Son saved man by living and dying as a man; He shares this salvation with humanity through a community of human beings, the Church; and He supernaturally joins individuals to Himself through means appropriate to our spiritual and material life, which are called sacraments. In Chapter VII, Adam writes:
“The Catholic cannot think of the good God without thinking at the same time of the Word made Flesh, and of all His members who are united to Him by faith and love in a real unity. The God of Catholicism is the transcendent, absolute God, who became Man for us in His Son, and therefore no solitary God, but the God of angels and saints, the God of fruitfulness and abundance, the God who with a veritable divine folly by the incomprehensible decree of His most free Will takes up into Himself the whole creation that culminates in human nature, and in a new, unheard of supernatural manner, “lives in it,” “moves” in it, and in it “is” (cf. Acts XVii, 28).”
Adam shows the essence of salvation to be communion, a share in the supernatural life of Christ that is given to us through the Church, “which is His body, the fullness of Him who fills all in all” (Ephesians 1:22-23), which baptizes us into the body of Christ (1 Corintians 12:12-13) and shares with us His life through sacraments like the Eucharist (John 6:52). Nor is salvation a solitary relationship between God and the individual; rather, it is the Christian’s adoption into a family of love, among fellow-children of the Father who, being in the body of Christ, share in His Sonship. Adam writes in Chapter VIII:
“As our Lord, in the great prayer which He taught His disciples, joined all who pray into a single unity and directed them to appeal out of this unity to their common Father, and as St. Paul especially enjoined prayer for one another (Rom. xv, 30; 2 Cor. i, 11; Eph. i, 15, etc.), so the Church prays, not in the name of any individual, nor as the mere sum of all individuals, but as a fellowship, as a priestly unity, as the visible priesthood of Christ.
“It is not I and you that pray, but the mystical Christ…”
This emphasis on the role of the Church as the whole Christ would become the ecclesiology of the encyclical Mysticum Corpus Christi (1943). Although it was downplayed after the “people of God” imagery of the 1960s returned the emphasis on the juridical, rather than the mystical, nature of the Church, Adam’s ecclesiology remains influential; and I myself believe that it helped pave the way for the rise of modern covenant ecclesiology and for Pope Benedict XVI’s emphasis on communion as the nature of the Church.
The Spirit of Catholicism by Karl Adam (translated by Dom Justin McCann, OSB, rev. edition) (Garden City, NY: Doubleday Image, 1954 [orig. 1924]) may be read online, legally and for free, at [LINKS REMOVED motu proprio PENDING COPYRIGHT CHECK.]. It is still on print in paperback here.
For more legally free ebooks, you may visit the Catholic eBooks Project.
[Update (8 April 2018): The links to online copies of the work have been removed, because we learned that the author died in 1966, i.e., much less than 70 years ago and hence not long enough in the past for his work to have passed into the public domain.]