When one buys a house that he finances with a bank, he signs a promissory note. He also signs a mortgage, which "secures" the obligation he undertakes to pay back what he borrows. (I would shorten the phrase "promissory note" to simply "note," but it would not be useful in this discussion to drop the word "promissory.")
The promissory note contains the promise of the borrower to pay back what he borrows, together with the interest, according to a time schedule described in the note. There is a mortgage, as I mentioned, but the core of the transaction is the borrower's promise which resides in the promissory note.
If the borrower were to break his promise (i.e. "default" on the promissory note) , the creditor could simply sue the borrower. There is no obligation that the creditor foreclose on the mortgage first. The creditor could simply sue and get a judgment.
However, in practice the creditor will foreclose, because the house will not run away and disappear, as the borrower might. Furthermore, in the course of the foreclosure proceedings, the creditor will get a judgment against the borrower anyway, if the proceeds of the foreclosure proceedings do not cover the borrower's indebtedness and the expenses of the foreclosure. The judgement is the "deficiency judgment" that I discussed in an earlier post.
Again, at the center of the mortgage foreclosure proceedings is the borrower's promise. There is nothing in the promissory note that states that "I promise, provided everything works out." It is simply "I promise."
It is important to point out that, if the foreclosure proceedings happen to yield more than the sum of what borrower owes and the expenses, (that is, the house sells for more than the mortgage balance) the creditor doesn't get to keep the profit. It goes to the borrower. Of course, in such a case the borrower porbably won't let his house go into foreclosure, because it has equity in it. After all, the creditor only agreed (promised) to take back what he lent, plus the interest. The creditor can't take the profit. We will hold the creditor to that promise.
The idea that the borrower can walk away, because the creditor has his remedies at law, and that there is, therfore, nothing immoral is nothing new, of course. It reflects the school of "legal realism," whose most famous advocate was Oliver Wendell Holmes, Jr. It pretty much reflected the philosophy at the University of Chicago when I attended the law school there, and I would say it reflected the philosophy of the other major law schools in the country. That philosophy is fraying at the edges, because its basis in Social Darwinism worries the Statists. Government, after all, needs to step into the economic jungle and impose "fairness."
But Christians don't take their cues from the pagan culture, regardless of how refined and sensible it seems to be (at least in a given case). We have to take a second look at these difficult questions. To coin a phrase, What would Jesus do?
What about Jesus? (By the way, he did not own a house here on earth but owned many of them elsewhere. Actually, here he did not have a place to lay his head. That's a little troubling when we worry about our houses here on earth.)
Maybe this question about keeping your promises in the financial context is a Caesar vs. God thing. Maybe Jesus refers to two worlds when he had answered the Pharisee's question and that Christians can walk back and forth between them when it makes economic sense to do so.