It is astonishing to hear a former Federal Reserve chairman acknowledge that he may have misled the public as part of an agreement with another senior government official about one of the most crucial moments in recent financial history — and that he now questions whether he should have “been more forthcoming.” But that is what Ben S. Bernanke says in his new memoir, “The Courage to Act: A Memoir of a Crisis and Its Aftermath.”

That crucial moment? The bankruptcy of Lehman Brothers. Mr. Bernanke, in perhaps the most candid explanation of Lehman’s 2008 collapse, writes that he and Henry M. Paulson, then the treasury secretary, purposely obfuscated when asked about Lehman’s demise early on, allowing a narrative to develop that the government had purposely let the firm fail.

“In congressional testimony immediately after Lehman’s collapse, Paulson and I were deliberately quite vague when discussing whether we could have saved Lehman,” Mr. Bernanke writes. “But we had agreed in advance to be vague because we were intensely concerned that acknowledging our inability to save Lehman would hurt market confidence and increase pressure on other vulnerable firms.”