Airing dirty laundry is pretty nasty when your neighbors peek out the back window and see the stains and filth. But, for our own purposes, it helps get rid of the stench and hopefully, puts the stuff to light to expose how bad the stains are. In our Christian home we extol the virtues of Martin Luther and gloss over some of the other stuff he's done or said chalking it up to age or uninformed. Here's a quote from Martin Luther's book "On the Jews and Their Lies" or rather Von den Juden und ihren Lügen which is outright wrong in it's approach to the Jews and completely antithetical to Paul's thinking. Forgive me for posting it, but this is for my records. The full book is here.Remember I am QUOTING and I by no means agree with Luther on what's below.

Jesus Christ is the preexistent Son of God who is both the creator of all things (John 1:1-3) and by whom all things are held together in place (Col 1:15-17) yet is also the one for whom all things were created (1 Cor 8:6; Rev 4:11). By His great power the heavens and earth were put in their place and by his might they will eventually be brought to a close (Heb 1:8-12). He is the firstborn, as in, the one of highest position of all creation. To Him belongs the glory (Heb 1:3) that belongs also to the Father (John 17:5) and belonged to Him from eternity past; Christ Jesus our Lord the preeminent one.

Rebecca has a post looking at the word propitiation, its usage and a challenge to figure out another word that can fit in its place. Unfortunately (or fortunately depending on your bend in modern bible translations) I'm all for the actual word propitiation but I also readily admit that there might be a shift of usage depending on the Biblical author. Paul might be making an allusion to the OT mercy seat and John may be referring to what the mercy seat offering accomplished in a general sense. So whereas Paul might be saying "God publicly (instead of behind a veil) revealed the place where God's wrath was turned away and satisfied in the person of His Son on the cross" John would be saying "Jesus Christ is the atoning sacrifice for the world, but for us believers especially."

Be that as it may, I'll play and try to update (if not dumb down) the actual word.

It would not be inconceivable to think that Paul is using the illustration of the potter and clay in a completely new way, or at the very least, a way unimagined by the readers of the Prophets. After all, many have argued that that is exactly what Matthew did (cf. Isa 7:14; Matt 1:23—young maiden vs. virgin). But I don't think that fits in with what Paul is doing.

While establishing the righteousness of God in the Gospel he makes a repeated effort in showing how the revelation of this righteousness is completely consistent with God's previous revelation of righteousness.