I have to get this off my chest. Macroeconomics is not economics at all. What little sense it makes can be traced directly back to the bits and pieces of microeconomic that is uses along the way.
I believe that Keynes was looking for a theory that would support his idea for how to fix a depressed economy. And his work is what justifies most of the government's fiscal policy to this day.
The problem is that his view of the macroeconomy is incomplete, illogical and, most troubling, it is static.