The Law has been ended for Christians, right? It came to an end as both finis and telos in Christ, and so can play no positive role in the lives of Christians...
That is a story told by many Christians and many Lutheran Christians among them, and it is so tempting because it is, in some specific ways, true, but it is also dangerous because it is a partial truth. A partial truth that can be dangerously misappropriated.
There are many problems with this notion, not the least of which is that its aggressive Paulinism can't seem to reckon with the data of the other Gospels and Epistles in a manner that is satisfactory for me at least...
Matthew 5:17, among other important texts, should make one leery of discounting the Law in a thorough manner that would totally abrogate its ongoing role and value, or so I am convinced.
Luther's Catechism is innocent of at least a strong form of this argument. The Commandments are, after all, the first segment of the Catechism and such a constituent element of it that ignorance of the Law would preclude one from "being reckoned among Christians" and admitted to the Sacrament of the Altar. That much is undeniable.
If I were pressed, I would say that Luther's entire Catechism is primarily concerned with the satisfaction of the First Commandment, and that he believes that this is exactly what Evangelical faith does (that is, satisfy the First Commandment). Following this assertion I would have to point out that the other commandments are viewed as ways and means for satisfying the First Commandment; the First split into a spectrum according to the manner in which it touches human life with God and human life with neighbor. It is hard to see how one could begin to understand Luther's own teaching about Evangelical faith without a thorough knowledge of the Commandments, their function and purpose.
I have recently seen the term "pedagogical use of the Law" used to describe the manner in which Luther understands the role of the Law in the Christian life. The Law teaches concrete ways in which a Christian may show forth his status as one who is redeemed by Christ and living out the saving faith that is in him. It teaches the shape of the Life in Christ by prescribing works (yes! Works!), which are truly God pleasing and God given works, that accord with it. There are some necessary assumptions at work here:
That the Commandments of the Law, though almost entirely stated as negative command, with important exceptions, each suggest a positive correlate. You shall not bear false witness necessary implies that you shall speak well of your neighbor and protect his reputation, etc.
That the Law can and should be utilized as a means for living a Christlike life because it is necessarily related to Christ. The Law not only has a single divine origin, but has also been perfected and fulfilled in Christ.
That human beings, under the influence of grace, can perform works of the Law that are truly God-pleasing, because they formally are so to God (their capacity to be pleasing is not determined by the one who undertakes them, but by their form as God given - except when one considers Christ as the primary actor who undertakes the Law, in this case, He overdetermines their capacity).
Luther is concerned to concentrate on this use of the Law for three reasons, one historical/theological, one more directly theological, and one of civil concern:
He is concerned to illustrate an alternative to the "works" generated by the medieval penitential system. These works have no direct support (if any support whatsoever) in the written Word of God, and therefore no sure foundation and therefore are ineffective means for pleasing God, and for comforting conscience. They are of a formally dubious value. The works prescribed by the Law, on the contrary, have both a secure foundation in the Truthful Word, thereby being formally sufficient, and therefore able to truly please God and comfort conscience.
He knows that the Law has a divine origin and is therefore integrally related to its origin. Because God is the author of all Good, The Law is Good and describes the conditions for a Good life.
That civil peace is necessary for the Good of mankind, and the spread of the Gospel, and the Law is related in some fashion to the natural Law that provides conditions for securing that peace. Further, that this Law must be known and inculcated in people.
Within Lutheranism, the teaching focus of the Law has been disputed among its various internal traditions. Some of those traditions make upholding some understanding of the positive ongoing value of the Law a matter of Confession (those that hold to the so-called "Third Use"), while others have denied any manner in which the Law can be viewed and utilized in such a fashion. This fact, I believe, has enormous consequences for the sort of theology that has been and is being done in these traditions. It is hard for me to see how those Lutheran schools that reject a "third use" do not inevitably end in one sort of antinomianism or another.
Why do I begin by discussing the "pedagogical use" or the "third use" of the Law? Because I think that this usage of the Law is the one that most naturally and organically appears in the Catechism, and, as the preceding has partially shown, the other uses are related to it. Foremost, it is the one that makes the most sense within the Catechism's own aims and goals. It is a practical work, concerned to show Christians the "what" and "how to" of the faith, and not primarily the "why". What do I need to know and do as a married man who is a Christian? Know the Commandments and practice chastity within the married estate, as the Sixth Commandment clearly teaches you!
Surely Luther emphasizes the so-called "second use" of the Law in many of his other works, and its importance cannot be overestimated, but I do not think that this use can so relativize and trivialize the "third use" as it appears in the Catechism.
So, now, finally, I think I am ready to turn to the First Commandment.