The same thing I have read all over and over again, if you say we are owing then who are we owing if not ourselves, USA is owing China, China is owing United Kingdom and the circle continues. So if we run out of cash as a result of debt, then we pay someone who initially lends us the loan then this same person because he is a capitalist, wont keep this money at home but will send it out and to make additional money for him or her which means the money is back in circulation. Unless the money is owed to someone not in this world again and its not coming back then I agree that the world will run out of cash or some of the countries will run out of cash.