Earlier this year, for instance, when the hedge fund manager David Einhorn was making his public case against Lehman (he now refuses to talk about the firm), he stressed his belief that Lehman was valuing its securities too high. He turned out to be exactly right.

Every time the market was roiled — especially after the Bear Stearns collapse — every firm on Wall Street had to re-mark their securities to reflect the new reality. That’s why you saw firms taking billion-dollar write-off after billion-dollar write-off, long after they thought they had taken care of the problem. And it is also why the write-offs will continue now that Lehman is bankrupt.

“Selling begets more selling,” said Sean Egan of the independent bond-rating firm Egan-Jones. And yet, even as they lowered the value of their mortgage-backed securities, firms like Lehman had still priced them too high. Back when he was talking publicly about Lehman, Mr. Einhorn used to cast Lehman’s mark-to-market pricing as an act of dishonesty. I tend to think it was more like wishful thinking. Either way, the result was the same.

A week ago, even as the government was bailing out Fannie and Freddie, Mr. Fuld went off to seek new capital — something Lehman desperately needed to shore up its decimated balance sheet — from the Korea Development Bank. Why did those talks break down? Because Mr. Fuld wanted more for Lehman than the Koreans thought it was worth. He simply couldn’t face the reality that his firm wasn’t worth what he thought it was.

Now look at his next-door neighbor, John Thain at Merrill Lynch. To be sure, Mr. Thain owned a better house — although Merrill Lynch also had billions in toxic securities, its bread-and-butter is its brokerage arm. It is fundamentally a gatherer of assets, not a bond-trader.

But there is another big difference between the firms. Unlike Mr. Fuld, who had run Lehman since 1993 and is the architect of the modern Lehman, Mr. Thain had been at Merrill Lynch just since December, when he was brought in to stanch the bleeding. He didn’t have the same pride of ownership in Merrill that Mr. Fuld had in Lehman. That is why he was willing to sell $31 billion worth of mortgage-backed derivatives for 22 cents on the dollar in late July — far lower than many firms had been pricing those securities.

And that is also why, seeing what had happened to Bear Stearns, Fannie and Freddie, and Lehman Brothers, he took the pre-emptive step of selling Merrill Lynch to Bank of America. In the process, he got $50 billion for Merrill’s shareholders. True, that was half of what Merrill was worth a year ago, and a once-proud name is about to be swallowed up by a commercial bank. But he also got $50 billion more than Mr. Fuld got for his shareholders — and being sold is a lot better than being liquidated.