Caronte, you say:
Suppose it is believed with absolute certainty that every 50 years, say every year divisible by 50, all debts are forgiven. There would follow a bunching of loan demand as the forgiveness date nears, while willing lenders would simultaneously vanish. The market would no longer match credit demand and supply, total welfare would suffer. Debt forgiveness would only avoid this problem if it was done by stealth, unpredictably, once and for all and never again. Like forgiveness of tax evasion or illegal buildings. Difficult to persuade debtors, (or builders, or taxpayers), that forgiveness would not occur again. Lots of people would be encouraged to borrow beyond what they can afford (or evade tax) – the moral hazard implication. Unsustainable indebtedness would multiply rather than disappear. Moreover, a defaulting borrower does not need forgiveness if she genuinely cannot pay: can’t pay, won’t pay, period. If the defaulting borrower has some residual wealth, though less than the outstanding loan, who is to deprive the creditor of that? What legal or moral right would support state action without creditor compensation?
Caronte, welcome, and many thanks for the length and thoughtfulness of your response. I don't pretend to have your economic expertise, but I still think there's a debate to be had. I'll try to tackle some of your points, not necessarily in strict order.
I suppose that in ancient Israel, the economy was not so monetised as today, so the advent of the year of Jubilee may not have been so disruptive as it would today. I don't really advocate a periodic debt cancellation - though I'm beginning to wonder about the necessity of charging interest. (Isn't it the case that some Swiss banks do in fact charge you for looking after your money securely, instead of making investments with it or lending it out to others?)
Competition between lenders may help keep down interest rates, but it's the ballooning of asset prices - and the consequent increase in the size of mortgage required - that causes the damage. So many are now locked into monster mortgages that a significant rise in interest rates - which otherwise might be appropriate for tackling inflation - is politically very unfeasible.
I argue that the price of houses is pretty much beyond the buyer's control, except that there's a point where a purchase is either not affordable (we seem to have reached that stage) or, as with subprime, fudged at the outset with disastrous consequences later. So I suggest the expansion of credit (for which, as you say, regulators also share responsibility), and the terms set by fee-hungry lenders and intermediaries, are more to blame than the family that wants a roof over its head it can call its own. Finance for cars and consumer goods is something else; a house is a necessity, and surely, owning one is not an unreasonable aspiration.
Banks should be, but are not being made to face the consequences - look how governments are propping-up Northern Rock and Bear Stearns.
Debt reduction does not seem unreasonable to me. If a life insurance company fails, the book of life business can be passed on to another provider, who is only required to underwrite 90% of the outstanding life cover. So why not for lenders who (through greed and stupidity) have gotten their sums wrong? A 10% reduction in the capital only represents a couple of years' interest. Better a borrower who repays a reasonable proportion of the loan, plus interest, than simply mail back the keys and leave the bank with illiquid stock it doesn't know how to manage.
Here in the UK, you can enter an agreement with creditors and as long as you keep up the scheduled payments, interest charging stops altogether. Maybe that would be another way forward - the monthly repayment would be lower and the borrower would see his equity in the house increase over time.
We've been watching enslavement by money-owners who have been licensed to print almost unlimited amounts of their own money, but the poor man only feels it going past and can save none, so remains in debt-bondage. Better any reasonable rearrangement, than "I owe my soul to the company store".