The Purloined Letter

"The aspects of things that are most important for us are hidden because of their simplicity and familiarity. (One is unable to notice something because it is always before one’s eyes.) The real foundations of his enquiry do not strike a man at all."

Wittgenstein, as cited by Oliver Sacks, The Man who Mistook his Wife for a Hat, Touchstone, 1970, p. 43