Thinking about the national debt.

Source: Per Research Center

"(A)s of the end of September 28.4% of the debt (about $4.76 trillion) was owed to another arm of the federal government itself."

  $2.76 trillion of the national debt is owed to Social Security. If the debt ceiling is not increased, what does it mean for Social Security? The Social Security payout began to exceed Social Security Pay-in in 2010, So I guess some social security checks and some medicaid payments now come from Social Security cashing in some treasury bonds. The treasury pays off current bonds and obtains funds for the government spending in excess of tax income by selling debt. If it can not increase debt, it can't raise all the money it needs. So what does it fund, and what does it fail to fund? It is legally responsible for funding the budget passed by the Congress and constitutionally obligated to honor debts.

Note that most of the national debt is owed to ourselves, not to China nor Japan. Note too that the debt began to fall as a portion of GDP in 2012, as the GDP increased.