Understand the meaning of "the light in the middle of the night is his companion", because it opens the way to light, and there are' four bleached walls'.

"It" refers to the midnight light. He should feel lonely with only a solitary lamp in the middle of the night, but Wen Yiduo is not. Under the illumination of a solitary lamp, he devoted himself to academic research and achieved remarkable results. Bleaching Four Walls is quoted from Wen Yiduo's poem Silent Night, which shows the poet's concern for the future of the motherland and the destiny of the people. The reference to "bleaching the four walls" in this paper is intended to show that Mr. Wen is engaged in academic research at night.