But this really ought to be a reflection on Friedman, not Keynes, so you don't need to worry about the details on those right now anyway. Here's Brad DeLong:
"Friedman Completed Keynes
The most famous and influential American economist of the past century died in November. Milton Friedman was not the most famous and influential economist in the world -- that honor belongs to John Maynard Keynes. But Milton Friedman ran a close second.
From one perspective, Milton Friedman was the star pupil of, successor to, and completer of Keynes’s work. Keynes, in his General Theory of Employment, Interest and Money , set out the framework that nearly all macroeconomists use today. That framework is based on spending and demand, the determinants of the components of spending, the liquidity-preference theory of short-run interest rates, and the requirement that government make strategic but powerful interventions in the economy to keep it on an even keel and avoid extremes of depression and manic excess. As Friedman said, “We are all Keynesians now.”
But Keynes’s theory was incomplete: his was a theory of employment, interest, and money. It was not a theory of prices. To Keynes’s framework, Friedman added a theory of prices and inflation, based on the idea of the natural rate of unemployment and the limits of government policy in stabilizing the economy around its long-run growth trend – limits beyond which intervention would trigger uncontrollable and destructive inflation.
Moreover, Friedman corrected Keynes’s framework in one very important respect. The experience of the Great Depression led Keynes and his more orthodox successors to greatly underestimate the role and influence of monetary policy. Friedman, in a 30-year campaign starting with his and Anna J. Schwartz’s A Monetary History of the United States , restored the balance. As Friedman also said, “and none of us are Keynesian.”
From another perspective, Friedman was the arch-opponent and enemy of Keynes and his successors. Friedman and Keynes both agreed that successful macroeconomic management was necessary - that the private economy on its own might well be subject to unbearable instability and that strategic, powerful, but limited economic intervention by the government was necessary to maintain stability. But, while for Keynes, the key was to keep the sum of government spending and private investment stable, for Friedman the key was to keep the money supply -- the amount of purchasing power in readily spendable form in the hands of businesses and households-- stable.
A relatively minor, technical difference in means, you might say. A difference of opinion that rested on different judgments about how the world works, which could (and ultimately was) resolved by empirical research, you might say. And you would be half right. For this difference in means, tactics, and empirical judgments rested on top of deep gulf in Keynes’s and Friedman’s moral philosophy.
Keynes saw himself as the enemy of laissez-faire and an advocate of public management. Clever government officials of goodwill, he thought, could design economic institutions that would be superior to the market -- or could at least tweak the market with taxes, subsidies, and regulations to produce superior outcomes. It was simply not the case, Keynes argued, that the private incentives of those active in the marketplace were aligned with the public good. Technocracy was Keynes’s faith: skilled experts designing and fine-tuning institutions out of the goodness of their hearts to make possible general prosperity -- as Keynes, indeed, did at Bretton Woods where the World Bank and IMF were created.
Friedman disagreed vociferously. In his view, it usually was the case that private market interests were aligned with the public good: episodes of important and significant market failure were the exception, rather than the rule, and laissez-faire was a good first approximation. Moreover, Friedman believed that even when private interests were not aligned with public interests, that government could not be relied on to fix the problem.
Government failures, Friedman argued, were greater and more terrible than market failures. Governments were corrupt. Governments were inept. The kinds of people who staffed governments were the kinds of people who liked ordering others around.
At the same time, Friedman believed that even when the market equilibrium was not the utilitarian social-welfare optimum, and even when government could be used to improve matters from a utilitarian point of view, there was still an additional value in letting human freedom have the widest berth possible. There was, Friedman believed, something intrinsically bad about government commanding and ordering people about -- even if the government did know what it was doing.
I do not know whether Keynes or Friedman was more right in their deep orientation. But I do think that the tension between their two views has been a very valuable driving force for human progress over the past hundred years."