Why did some of the most brilliant minds of the last century become apologists for history's worst tyrannies? Today we cringe recalling the 1968 pronouncement of Chinese-born author Han Suyin, who died last Friday aged 95, that Mao Zedong was "the greatest man China has known".
In her time, she defended the Great Leap Forward, which induced the famine that has been described as the worst man-made disaster in history, and the Cultural Revolution, which even the Chinese Communist Party has now repudiated.
Perhaps it's not fair to judge her by what we know about Mao today, as many foreigners and fellow travellers besides Han regarded Mao as a great man then. But still, she cannot be completely absolved of a wilful blindness.
A doctor who could speak and write in Chinese, English and French, she had all the intellect she needed to see Mao's China for what it was, rather than what she hoped it would be.
Han is nowadays mostly remembered as the author of an autobiographical novel that inspired the 1950s Hollywood hit movie Love Is a Many-Splendored Thing, starring William Holden and shot almost entirely in Hong Kong. But she wrote dozens of books, including two biographies of Mao and Zhou Enlai .
Just as Edgar Snow introduced Mao to the West before he came to power, Han's endorsement helped legitimise the Great Helmsman's rule for many Westerners even as he exercised supreme command and plunged the nation into chaos again and again.