In The General Theory, Maynard Keynes said
we can draw the line between "money" and "debts" at whatever point is most convenient for handling a particular problem.
In Capitalism and Freedom, Milton Friedman wanted
to carefully manage the quantity of money, but he didn't care what money was managed, what monetary aggregate. It didn't concern him at all.
According to Keynes, where you put the dividing line between money and debt depends on the problem you're trying to solve. According to Friedman, it doesn't matter where you put the dividing line.