同床异梦

Origin and story

In a letter to Zhu Xi, the Southern Song writer Chen Liang describes several rooms at his home and poems friends had written about them. He feels that the poems, despite their skill, have not fully expressed his intentions. Even people sleeping in the same bed, he observes, have dreams of their own; there is no need to keep comparing him with ancient figures such as Zhuge Liang.

The wording in the letter is 同床各做梦, rather than the later compact idiom. A related image also occurs in Chan Buddhist discourse. The shared bed makes a useful contrast between outward closeness and inward difference. Later usage often gives that difference a sharper edge: partners appear united but pursue incompatible aims.