Quantum mechanics is humanity's finest scientific achievement. It explains why the sun shines and how your eyes can see. It's the theory behind the LEDs in your phone and the nuclear hearts of space probes. Every physicist agrees quantum physics is spectacularly successful. But ask them what quantum physics means, and the result will be a brawl. At stake is the nature of the Universe itself. What does it mean for something to be real? What is the role of consciousness in the Universe? And do quantum rules apply to very small objects like electrons and protons, but not us? These are not just academic debates--they are both questions as profound and rich as those that motivated Plato's allegory of the cave or Descartes's claim that to think is to be, and puzzles that must be solved if physics is ever to replace its stopgap description of the universe (which quantum mechanics surely is) with a final, truer one.For years the dominant interpretation was the Copenhagen interpretation, promulgated and enforced by Niels Bohr and his followers: it privileged randomness and consciousness above all else, essentially arguing that nothing was certain, and nothing was truly real unless it had been measured. And they were ruthless--for forty years and more, Bohr and his minions actively undermined the careers of anyone who challenged them, supported by a military-sponsored establishment that cared about little more than building bigger bombs. In What is Real?, Adam Becker brings to vivid life the brave researchers whose quest for the truth led them to challenge Bohr: David Bohm, who picked up Einstein's mantle and sought to make quantum mechanics deterministic, all while being hounded by the forces of McCarthyism; Hugh Everett, who argued that everything, big and small, must be governed by the same rules; and John Bell, who went to great lengths to eradicate the power of the god-like observer from the core of quantum physics. And they paid dearly, their reputations, careers, and sometimes lives ruined completely. But history has been kinder to them than their contemporaries were. As Becker shows, the brave intellectual giants have inspired a growing army of physicists and philosophers intent both on making a philosophically more satisfying theory of the universe and a more useful one as well. A gripping story of some of humanity's greatest ideas and the high cost with which many have pursued them, What is Real? is intellectual history at its passionate best.