Cory Doctorow explained modern monetary theory to me last year while we were in my kitchen. It changed my attitude towards balanced budgets and national deficits. If you would like to read Cory's explanation of modern monetary theory, he wrote it on his website today.
If governments are the source of money, then they don't tax us in order to spend. They spend (which puts money into the economy) and then tax back.
If the government runs a "balanced budget" that means it's taxing as much money of out existence as it is spending into existence, leaving behind no money for the rest of us to save or spend. Balanced budgets starve the private sector of the money it needs to operate.
He also recommends this podcast interview with Stephanie Kelton, author of The Deficit Myth: