Economists set themselves too easy, too useless a task if in tempestuous seasons they can only tell us that when the storm is past the ocean is flat again.
Black’s theories, and the other rational-expectations attempts to explain business cycles, arose at a time (the 1970s) when economic policy-makers had probably come to overemphasize the storm-mitigation aspect of their jobs at the expense of long-run considerations like growth and productivity. But again, the Keynesian attitude seems more appropriate to our current situation than the Blackian one. (Emphasis on seems. I certainly don’t know this.)