Firstly, Peter Leithart is Against Christianity (pp. 31-32):
Ask the average Christian about the relationship between the "church" and "salvation," and you are likely to get one of two answers: either (if the Christian is a rather old-fashioned Roman Catholic) that the Church is a reservoir of salvation, to which one must repair to receive grace; or (if the Christian is a rather common sort of evangelical) that salvation occurs apart from the Church, though it is a help along the way.
Despite the apparent differences between these two views, they are fundamentally similar. Both conceive of "salvation" as a something (almost a substance) that can be stored in a reservoir or infused into sinners directly by God. Both believe that the whole point is the salvation of individuals: for the Catholic, the Church is an essential conduit of grace, but salvation is what happens to the individual. For the evangelical, the Church is a nonessential aid to individual salvation. In both cases, [Gnostic] Christianity is looming in the background.
Biblically, however, salvation is not a stuff that one can get, whether through the Church, or through some other means. It is not an ether floating in the air, nor a "thing," nor some kind of "substance." "Salvation" describes fallen creation reconciled to God, restored to its created purpose, and set on a trajectory leading to its eschatological fulfillment. Ultimately, "salvation" will describe the creation as a whole, once it is restored to God and glorified (Rom. 8:18-25). Grammatically, "salvation" is a noun; theologically, it is always adjectival.
Nor is salvation adjectival merely of individuals. If salvation is the re-creation of man through Christ and the Spirit (which it is), then salvation must be restored relationships and communities as much as individuals. If Christ has not restored human community, if society is not "saved" as much as the individual, then Christ has not restored man as he really is. Salvation must take a social form, and the Church is that social form of salvation, the community that already (though imperfectly) has become the human race as God created it to be, the human race that is becoming what God intended it to be.
The Church is neither a reservoir of grace nor an external support for the Christian life. The Church is salvation. [source]
And secondly, Peter Leithart is Against Sacraments (pp. 75-78):
Six overlapping tendencies make it difficult for evangelicals to grasp baptism and the Lord's Supper.
First, a spiritualizing reading of redemptive history: "When Jesus removed the special status of Jerusalem as the place where God was to be worshipped (John 4:7-24), he signaled the abolition of all material forms that constituted the typological Old Testament system." The move from Old to New is thus seen as a move from ritual to non-ritual, from physical to less physical forms of worship. Baptism and the Supper seem anomalous throwbacks to an earlier era: what use do "spiritual" churches have for these rituals?
Second, the prophets: Israel's prophets inveighed against empty formalism, and some conclude from this that the prophets condemned form and ritual as such.
Third, the Reformation: The Reformers taught that the Word has priority over the sacraments. Salvation comes from hearing the Word with faith, not by mechanical adherence to the sacramental system of the Church. Sacraments are an "appendix" to the Word.
Fourth, individualism: The frame of reference for nearly everything, including worship and sacraments, is the individual person and his experience of the world. So, in sacramental theology we ask questions like, "What benefit do I receive from the sacrament?" or "What grace does the individual child receive from baptism?" And we wonder why we need these objects and substances to communicate these benefits.
Fifth, inwardness: Grace is invisible, so why do I need visible substances to receive grace? Moreover, what is really important is my spiritual heart-relationship with God; my outer physical action are of lesser significance. What matters is the "me" lurking behind the roles I play and the things I do. What happens on the outside never touches that inner self that is unchangeably me. What good then is external bath, physical food?
Finally, privatization: Religion is a matter of belief and personal devotion. Public rituals can be faked, and so those who tie religion to public rituals tempt us to be hypocrites.
In the end, all these factors reduce to one: the Church has embraced modernity's disdain for ritual, though we have given pious glosses to our worldliness.
In the end, all these factors are part and parcel of our adherence to Christianity.
Baptism and the Supper as appendixes to the Word: Despite its venerable pedigree, this is not a useful way to approach the issue. We are able to understand the Word without the help of appendix, as we can read many books with profit without reading the appendix. So long as baptism and the Supper are seen as "appendixes," they will be seen as expendable. Characterizing baptism and the Supper as "appendixes" to the Word, further, is part and parcel a Protestant tendency toward the "primacy of the intellect." It is rationalism, in that it reduces baptism and the Supper to a means for communicating information. But that is not what rituals are for. Treating baptism and the Supper as disguised sermons reduces them so they can be encompassed and tamed by Christianity.
Individualism: As God is one and three, as God's being is being in communion, so human being is being in communion. Made in the image of the triune God, we are always embedded in networks of relationship, long before we are conscious of that fact. Before we could talk or "make up our own mind," we were addressed, talked to, kissed, smiled at. The only individuals in the Bible are idols and their worshippers, who have all the equipment for relating to others and the world but cannot make use of it (cf. Ps. 115). Because of our individualistic bias, we cannot recognize that the "sacraments" are rituals of a new society, public festivals of a new civic order. And, individualism is part and parcel of the heresy of Christianity.
Religion and interiority: This has a certain plausibility because Scripture does talk about inner man and outer man, about body and soul. Yet, Scripture makes no hard or absolute demarcation between inner and outer. When people eat and drink, Scripture says their "souls" are refreshed (e.g., 1 Sam. 30:12), and exterior discipline of our children purges foolishness from their hearts (Prov. 22:15). So, outer events invade the inner life. And, inner things come to outer expression, for out of the thoughts of the heart come murders, adulteries, and other evils (Mk. 7:20-23). The mere fact that the Bible often names the "inner" man by reference to bodily organs (heart, kidneys, liver) is a hint that Scripture does not sharply distinguish inner spiritual from outer physical realities; even the "inner" man is conceived physically, not as an unbodied, ghostly self. Scripture thus teaches a complex interplay of inner/outer in human existence, a duality within unified human being. There is more to us than appears on the surface but human being is always "being in the world" because it always means "being a body." Whatever else we might say about a baptized person, we can say with utter confidence that he is baptized, and this is an irreversible moment in his "being in the world."
Religion is private: This is the heresy of Christianity in a nutshell. [source]
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