I was looking around at the new Ecclesia Augustana blog (it seems to be a group of college student fixated on the anti-objective justification heresy) and I came across this post:
The gist of what is said here is as follows: Polycarp Leyser states that faith is the "instrumental cause" of justification. The theologians of the old Synodical Conference said that it was God's Word and the merit of Christ that was the cause of justification, and not faith in and of itself. Hence, they are out of step with orthodox Lutheran theology and wrong.
This post is very odd because Daniel Baker (the person who wrote it) is apparently unfamiliar with Aristotle's metaphysics and his scheme of four causes (formal, material, efficient, and final). I leave it to the reader to look these up, but put succinctly: If faith were the sort of cause that they want it to be in regard to justification, it would probably be an efficient cause of justification. But Polycarp Leyser doesn't say that. Rather, he says that faith is an "instrumental cause" (a finer categorization of the categories of cause, divised by the medieval scholastics). An instrumental cause is a means or organ through which the efficient cause or agent actualizes the reality. For example, a hammer is the instrumental cause of a table. It is used by the efficient cause (the acting agent, the carpenter). It isn't the idea what what a table is (formal cause) or the wood the table is made out of (material cause). Neither is it an acting agent (the efficient cause). Rather it is merely the passive means through which the material receives its shape based on the idea of the mind of the builder. Consequently, Leyser is stating that faith is merely a passive receptacle for the already existing reality of justification, which is to be found in the gracious will of God and in the merits of Christ distributed through God objective word of promise made manifest in Word and sacrament.
Therefore, not knowing this, Baker has totally misinterpreted the quotation as being in favor of the anti-OJ position, when really it's in favor of OJ! If faith is merely an organ or instrument, then justification is a reality that pre-exists faith. Faith is therefore only a means of receiving this reality.
Moreover, Baker ridicules Walther and the other theologians of the Synodical Conference for not understanding that faith causes God's verdict of justification. Nevertheless, when the term "instrumental cause" is understood correctly, Walther and the rest of them are vindicated. Also, it should be noted that these theologians do in fact did use the term to describe how subjective justification is actualized. Walther and the rest of the Syncon theologians say this on a number of occasions (when they are getting technical). Also, it should be observed, that the Baier Compendium (which Walther used in seminary instruction before they had Pieper) describes justification in basically this way. Here we read:
"The instrumental cause of our faith are the words of the Gospels and baptism." (Baier, 3.11)
In other words, the reality of God's grace in Christ is merely channeled to faith through the means of grace (instrumental causes). Our faith doesn't cause it's reality, it just receives it through the instruments. Again we read in the next chapter on justification:
"6. The efficient cause of the act of justification is the triune God. 7. The internal impulsive cause is the goodness or free grace of God. 8. The external impulsive cause, and the principal and meritorious cause, is Christ the mediator, by reason of his active and passive obedience. 9. The lesser principal impulsive cause [a Protestant scholastic sub-category of instrumental cause] is faith in Christ. 10. Besides this faith truly nothing else is able to be held on our part as part of the cause of justification." (Baier, 4.6-10)
There are a number of posts like this on the website, that is, where the author being cited is badly misunderstood because of unfamiliarity with the source material (the one on Augustine's understanding of 1 Cor. is chief among these!).
I have a suggestion: before a person starts making pronouncements about what the orthodox fathers said (while insulting Walther, who knew them very well, in the process!), bother to read their sources and understand their theological method! It's also very important to know how certain theological and philosophical terms are being used. There are many good books out there on theological methods and terminology among the Lutheran fathers.