"Of the three great skeptics I interviewed, Popper was the first to make his mark. His philosophy stemmed from his effort to distinguish pseudoscience, such as Marxism or astrology or Freudian psychology, from genuine science, such as Einstein's theory of relativity. The latter, Popper decided, was testable; it made predictions about the world that could be empirically checked. The logical positivists had said as much. But Popper denied the positivist assertion that scientists can prove a theory through induction, or repeated empirical tests or observations. One never knows if one's observations have been sufficient; the next observation might contradict all that preceded it. Observations can never prove a theory but can only disprove, or falsify it. Popper often bragged that he had "killed" logical positivism with this argument."

“Our descendants will learn much more about nature, and they will invent gadgets even cooler than smart phones. But their scientific version of reality will resemble ours, for two reasons: First, ours… is in many respects true; most new knowledge will merely extend and fill in our current maps of reality rather than forcing radical revisions. Second, some major remaining mysteries—Where did the universe come from? How did life begin? How, exactly, does a chunk of meat make a mind?—might be unsolvable.”

“In Theories of Everything... John Barrow argued that Gödel's incompleteness theorem undermines the very notion of a complete theory of nature. Gödel established that any moderately complex system of axioms inevitably raises questions that cannot be answered about the axioms. The implication is that any theory will always have loose ends. Barrow also pointed out that a unified theory of particle physics would not really be a theory of everything, but only a theory of all particles and forces. The theory would have little or nothing to say about phenomena that make our lives meaningful, such as love or beauty.”

“Feyerabend's Dadaesque rhetoric concealed a deadly serious point: the human compulsion to find absolute truths, however noble, too often culminates in tyranny. Feyerabend attacked science not because he truly believed that it had no more claim to truth than did astrology. Quite the contrary. Feyerabend attacked science because he recognized—and he was horrified by—its power, its potential to stamp out the diversity of human thought and culture. He objected to scientific certainty for moral and political, rather than for epistemological, reasons.”

“By the time I was 11 or so Catholicism stopped making sense. Why, if God loves us, would He inflict hell on us, just for skipping mass now and then? That doctrine, which hard-eyed nuns taught in catechism, seemed awfully harsh. Also, I couldn’t imagine how heaven could fail to be boring. Like lots of young people in my generation , I began checking out more exotic religions. I became intrigued by enlightenment, the goal of Hinduism and Buddhism. I envisioned it as a state of supreme bliss and wisdom. It’s like heaven, except you don’t have to die to get there. Seeking enlightenment, I learned meditation and yoga and ingested psychedelics, and I read Doors of Perception by Aldous Huxley and Siddhartha by Hermann Hesse. Far from enlightening me, my forays into mysticism deepened my sense of weirdness.”

“Of course, the apparent disarray could have stemmed entirely from my own ignorance. But when I revealed my impression of confusion and dissonance to one of the attendees, he reassured me that my perception was accurate. “It’s a mess,” he said of the conference . The problem, he noted, arose because, for the most part, the different interpretations of quantum mechanics cannot be empirically distinguished from one another; philosophers and physicists favor one interpretation over another for aesthetic and philosophical—that is, subjective—reasons.”

“One of the things that makes Gell-Mann so insufferable is that he is almost always right.”