I've never seen anyone suggest that growth in productivity might be the fuel for a growth in debt. The rate of productivity growth has been remarkable in the last couple of decades. So has the growth in debt. Maybe the one causes the other. And maybe debt is the result of a good thing (productivity growth) and not a bad thing (a sudden lapse in morality).
Try this thought experiment.
100 people all farm to eat. Then one day, one guy makes a machine that allows him to feed 100 people all by himself. Now, we've created 99 unemployed people who can only beg or borrow in order to eat.
One of two things happens next. Either no one else comes up with new products or services that generate income and the the starving 99 are unable to pay back the inventor, and the whole "economy" collapses back to some uneasy situation with 99 parasites and one productive inventor. Or two, inventors and entrepreneurs emerge from within the 99 to create new goods and services that allow them to eventually pay back the loan for food and create more jobs.
If we stop short at the debt of the 99 hungry hopefuls, we'll be stuck. The way through this is not to take on less debt but, rather, take on more.
This odd little thought experiment suggests that debt - whether of the newly unemployed who want to eat or of the new and would-be inventors and entrepreneurs - follows from productivity gains. And the debt may be really ugly. For instance, in this example, the unemployed food eaters are borrowing money to eat. And the "wealth" the inventor feeding 100 people has is in the form of IOUs from the hungry hopeful. And further, if the successful inventor backs a new inventor, he is actually loaning him money that is just promissory notes and not real cash. And yet if all these loans are not made, the system collapses.
Following this logic, it could be that debt follows from productivity gains. The point then is to stimulate more innovation - even if that means incurring more debt - in order to create the next venture that will provide jobs to the newly unemployed.
So, what is the solution to our current levels of unemployment and increased debt? It is not to worry about debt. It is to worry about creating the next new thing - from building infrastructure to creating new businesses.
I will maintain my contention that our problem is not a problem of too much debt or even of financial institutions that create too much wealth - real or bubbled. Our problem is that we aren't doing enough to translate our excess labor and capital resources into new ventures. This is not a failure of labor or capital markets. It is a failure of entrepreneurship. We need to do more to create entrepreneurship within organizations (what Gifford Pinchot calls intraprenuership) and without. The solution is that simple and that complicated. Focusing on debt right now is a distraction. We need to innovate our way out of this.
Which means, essentially, we're in the same situation we've been in for centuries, only more so.