Atlas Shrugged. Ayn Rand

Thinking is man's only basic virtue, from which all the others proceed. And his basic vice, the source of all his evils, is that nameless act... of blanking out, the willful suspension of one's consciousness, the refusal to think—not blindness, but the refusal to see; not ignorance, but the refusal to know. It is the act of unfocusing your mind and inducing an inner fog to escape the responsibility of judgment...

Non-thinking is an act of annihilation... an attempt to wipe out reality. But... reality is not to be wiped out, it will merely wipe out the wiper. By refusing to say 'It is,’ you are refusing to say 'I am.' By suspending your judgment, you are negating your person. When a man declares: 'Who am I to know?'—he is declaring: 'Who am I to live?'