From Galt's speech in Atlas Shrugged:
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 which all of you
practice, but struggle never to admit: the 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—on the unstated premise that a thing will not exist if only you refuse to identify it, that A will not be A so long as you do not pronounce
the verdict “It is.” Non-thinking is an act of annihilation, a wish to negate existence, an attempt to wipe out reality. But existence exists; 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?