Skidelsky takes a more systematic approach, dividing Keynes’s thinking into its political, economic and moral elements. In this telling, Keynes’s political views were dominated by a pragmatism similar to what Clarke describes, where the best is the enemy of the good. Keynes was no socialist, but also no free-market ideologue. He was interested in what worked.

In economics, the crucial Keynesian concept is uncertainty. Where it prevails, the simple rules of classical economics don’t apply. That’s because the classical economics that both predated Keynes and superseded him relies on rational actors making rational assessments. In order to make such assessments you have to have reliable knowledge, usually derived from past experience. Buyers of oranges or newspapers or legal services can be said to possess such knowledge. Buyers of speculative securities cannot. They’re always looking into an uncertain future, “anticipating what average opinion expects the average opinion to be,” as Keynes put it.

This, in Skidelsky’s convincing telling, is why financial markets are so prone to disorder and disaster. It’s not that investors are terribly irra­tional. It’s that no one can really know what rational means when it comes to pricing investment securities. That’s why relying on financial markets to make big economic decisions can be so problematic, and why economic theories built on the assumption that financial markets behave ration­ally fail to explain our world. Skidelsky is of the opinion that graduate education in economics should be sharply divided into micro­economics, in which students single-mindedly focus their mathematical and logical skills on problems that aren’t dominated by uncertainty, and macroeconomics, which requires a more varied humanistic training.

If economics does not contain all the answers, where are we to find them? This was a question to which Keynes gave a lot of thought. As a young man he was highly influenced by the teachings of the Cambridge philosopher G. E. Moore, who preached that we should strive for a “good” that was neither moral nor hedonistic (nor even definable). Later on, Keynes was to acknowledge that this “good” might be a less elegant concept than he had once thought. He and his Bloomsbury friends believed for a time that they had discovered a modern, secular set of ideals, but may simply have been embroidering on the Christian tradition of their parents. As he wrote to his friend Virginia Woolf, “We destroyed Xty & yet had its benefits.”

In a famous 1930 essay, “The Economic Possibilities for Our Grandchildren,” the grandchildless (and childless) Keynes sketched a distant, “Star Trek”-like future where once “the economic problem was solved,” people could focus on the things that mattered most. But what mattered most? Keynes had no real answer for that and could see that coming up with an answer would be a fraught and dangerous task for most societies. But just by trying to address it, he made his economics a very different subject than the single-minded pursuit of resource-maximization that calls itself economics today.