Daily Chinese Idiom Guessing Game
To believe something to be true without question or verification.
相信他是真的。指把假的当作真的。
明·冯梦龙《醒世恒言·李沠公穷邸遇侠客》只因他平日冒称是宰相房玄龄之后，在人前夸炫家世，同僚中不知他的来历，信以为真，把他十分敬重。”
He heard the rumor and took it for truth without checking any facts.