Eric Hoffer (1902-1983) was a longshoreman & philosopher in America. When he was 5 years old, his mother fell down with him from a flight of stairs. 2 years later, he lost his eyesight. He stayed blind in his childhood, but he restored his eyesight at age 15 by some miracle. He became a voracious reader fearing he would go blind again.
He says in his book Reflections on the Human Condition (1973):
An empty head is not really empty; it is stuffed with rubbish. Hence the difficulty of forcing anything into an empty head.空っぽの頭はほんとうに中身が空っぽなのではない。空っぽの頭の中にはゴミがぎゅうぎゅうに詰め込まれている。よって、空っぽの頭に何かを詰め込むことは困難なのだ。