For simplicity's sake I have crunched ALL of economics into just two laws (here). You understand these two laws and you understand the economic way of thinking.

Keynes broke the first law (that there is no free lunch). Hence he was a fool, not an economist. But by his popularity he set in train a process by which thousands of "macro-economists" started imagining that they could break the first law of economics, just like fool "physicists" who imagine they have discovered a perpetual motion machine. 

For those of you who (still!) believe that the government can borrow (thus print) endless amounts of money to "create" jobs and prosperity (and there are only a handful of economists alive today who don't "believe" in this), here's a cautionary piece of advice Peter Boettke, from one of the most sensible economists:

Keynesianism broke the old time fiscal religion of balanced budgets and fiscal responsibility, and changed not only attitudes of economists and policy makers, but also eroded whatever institutional constraints existed on public spending that had existed.  Keynesianism cannot work to solve our current problems because Keynesianism is responsible for our current problems.

Read his whole article here. Also his citation – of James M. Buchanan.

That Keynes also broke the second law of economics should be self-evident, as well.

Related posts:

1. London School of Economics radio debate on BBC: Hayek vs Keynes
2. Waiting for the public broadcast of the London School of Economics debate: Hayek vs Keynes
3. Dorian Electra is electrifying the teaching of economics. What chance does Keynes have now?
4. Marx and Keynes were not scientists but cult leaders
5. America is almost broke, with (almost) no capacity to become solvent again
6. Keynes was no economist at all: a foxy Fabian socialist
7. Continuing the Keynes debate. Have I gone overboard?
8. Keynes, “the academic idol of our worst cranks and charlatans”
9. Is a re-union of the two churches of economics in the offing?
10. Keynes the incompetent economist