i understand its a very basic analogy and it has its flaws, but im sorry, i just dont buy Keynesian economics i believe in the Austrian School who have predicted everything that has happened so far... but time will tell if Keynesian economics does work (it hasnt yet).
You've used an analogy - i'll use a similar one. Let's say you have a business that owes £20k, and has £5k in the bank. The business can choose to pay off a large chunk of the debt... *or* it can choose to employ (spend) that £5k in a way that returns more money in the long term - this could be on marketing, or newer more efficient equipment, for example. "Return on Investment" is what you're looking for...