I was really excited to read about economics for today. I've wanted to take Econ 110 for a while now (sometimes I need to take a class in order to make myself learn it) and having an intro to some of the thought is great!
My second brother, who is currently 14, is vehemently against Keynesian economics. As I understand it, Keynesian economics promotes government intervention in the economic system because as Keynes (and/or his promoters) believes, the economic system is inherently unstable, and the government is not. Therefore, stability needs to be added to the economic system of a country from the government itself in order to maintain order.
I found it interesting that in the reading, it mentions how this seemed to work very effectively around the time of Keynes, back in the time of the Great Depression and going into WWII. Of course, since the economy was so poor at this point, many people jumped on board and supported this philosophy. However, as the economy got better overall, people began to see the poor consequences of sticking solely to this strategy over the long-term - the government began to lose its economic stability as it became increasingly in debt, and thus is beginning to lose its own economic stability.
My personal, naive, and uneducated opinion is that a mixture of economic philosophies is often what's best to maintain economic stability. In each different situation, people are going to behave differently, and thus it's hard to use one algorithm to keep the economy constant or improving. This is what makes economics so difficult for government to agree upon!