Edward Fredkin

• 1. Introduction

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  Edward Fredkin bought chemistry supplies at age 10, made his own fireworks in Los Angeles, and got in trouble because fireworks were illegal. That detail captures something essential about the man. He was constitutionally incapable of waiting for permission to explore an idea.

  Fredkin was born on the 2nd of October, 1934, and he would spend the next nine decades pushing into territory where formal credentials were not required and formal credentials were sometimes not held. He never graduated from college. He dropped out of Caltech partway through his sophomore year. Yet Marvin Minsky recruited him to MIT as a full professor in 1968, and he would go on to hold positions at Carnegie Mellon, Boston University, and Caltech before he died on the 13th of June, 2023, at the age of 88 in Brookline, Massachusetts.

  His contributions range from a fundamental data structure used in computing to this day, to a philosophical claim that all of physical reality is, at bottom, a computation. Along the way he invented an interrupt system that transformed computer hardware, founded companies across industries from film scanning to sea water desalination, and spent a year at Caltech teaching a Nobel Prize-winning physicist about computers while learning quantum mechanics in return.

  Who was this man? How did a dropout fighter pilot reshape the theory of computation? And what exactly does it mean to say the universe runs on information?

• 2. A Childhood Built on Hustle

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  Fredkin's mother was a concert pianist who never performed professionally, and his father had lost everything in the 1929 stock market crash. Both parents were Russian-Jewish immigrants who met in Los Angeles. The family lived with relative poverty, and when Fredkin was 11 his mother died from cancer. For stretches of his childhood he lived with other families or with his older sister, until his father remarried.

  He handled a large newspaper delivery route to earn money. He graduated from John Marshall High School a semester early, specifically so he could accumulate funds for Caltech tuition and living expenses. When Caltech later admitted him, they told him he had entered with the worst high school grades they had ever seen. He did poorly in school not because he lacked ability but because he refused to do homework.

  He quit Caltech partway through his sophomore year. In 1952, rather than risk being drafted into the Korean War, he joined the United States Air Force to train as a fighter pilot. That decision, aimed at staying alive and keeping control of his own path, is what put him in front of a computer for the first time.

• 3. From Fighter Pilot to Programmer

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  In 1956, the Air Force assigned Fredkin to MIT Lincoln Laboratory, where he worked on the SAGE computer. That posting ended his formal military trajectory and began his computing career. On completing his service in 1958, J. C. R. Licklider hired him to work at the research firm Bolt Beranek and Newman, known as BBN.

  At the Eastern Joint Computer Conference in Boston in December 1959, Fredkin saw the PDP-1 computer prototype. He recommended that BBN purchase the very first PDP-1 to support research projects. When the machine arrived, it came with no software whatsoever. Fredkin wrote an assembler language for it called FRAP, which stood for Free of Rules Assembly Program, and also wrote its first operating system.

  Working directly with Ben Gurley, the designer of the PDP-1, Fredkin designed significant modifications to the hardware to support time-sharing. He invented and designed what Digital called the "Sequence Break" - the first modern interrupt system. An interrupt system allows a computer to pause a running task when something more urgent demands attention. It is now a foundational feature of every modern computer.

  He also organized and founded the Digital Equipment Computer Users' Society, DECUS, in 1961. That organization created a community around the PDP-1 at the moment the machine was just becoming real.

• 4. The Entrepreneur in the Machine

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  In 1962, Fredkin founded Information International, Inc., an early computer technology company that developed high-precision film-to-digital scanners, along with other leading-edge hardware. The company went public and Fredkin became a millionaire.

  The pattern of company-founding never stopped. Over the course of his career he served as founder or CEO of Three Rivers Computer Corporation, New England Television Corporation - which owned Boston's then CBS affiliate WNEV on channel 7 - and The Reliable Water Company, a manufacturer of advanced sea water desalination plants. The range is striking: computing hardware, television broadcasting, water infrastructure. The common thread was Fredkin's appetite for applying technology to concrete problems in the physical world.

  His inventions were similarly wide-ranging. He invented the trie data structure, independently of Rene de la Briandais, who published a year earlier. He invented radio transponders for vehicle identification and developed the concept of computer navigation for automobiles. He also worked in computer vision and chess, both of which fell under the broad umbrella of artificial intelligence research.

  The 1984 Carnegie Mellon University Dickson Prize in Science recognized his contributions, and in 1999 CMU established the Fredkin professorship in his name.

• 5. Teaching Feynman, Learning Quantum

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  Marvin Minsky, whom Fredkin had first met at BBN, recruited him to MIT in 1968 as a full professor despite the fact that Fredkin had never graduated from college. From 1971 to 1974, Fredkin served as Director of Project MAC at MIT, the laboratory that was later renamed the MIT Laboratory for Computer Science in 1976.

  After MIT, Fredkin spent a year at Caltech as a Fairchild Distinguished Scholar. During that year he taught Nobel Prize-winning physicist Richard Feynman about computing, while Feynman taught him quantum mechanics. The exchange was bilateral and serious: two thinkers at the height of their powers each offering the other a window into a different discipline.

  He then spent six years as a professor of physics at Boston University. His later academic interests centered on digital mechanics, which is the study of discrete models of fundamental processes in physics. His associations with Carnegie Mellon University spanned several decades and included a Distinguished Career Professor of Computer Science position and a Distinguished Career Professor of Robotics appointment.

• 6. Reversible Computing and the Fredkin Gate

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  Fredkin's deepest technical work concerned reversible computing. A reversible computation is one where you can run the process backward and recover your original inputs. Most computation destroys information as it goes. Fredkin argued that this destruction was not inevitable, and that it had implications for the physics of computation.

  Konrad Zuse's book "Calculating Space" in 1969 had mentioned the importance of reversible computation. But according to Fredkin's colleagues and the field's history, the Fredkin gate represented the essential breakthrough. A logic gate is a basic building block of digital circuits; the Fredkin gate is one that can be run in reverse without losing information.

  He also invented the Billiard-Ball Computer Model for reversible computing, a theoretical model in which computation is performed by colliding billiard balls, demonstrating that computation could in principle be done with no energy loss. He invented the SALT Cellular Automata family as well. Dan Miller designed and programmed the Busy Boxes implementation of Salt, with assistance from Suresh Kumar Devanathan. The early SALT models are reversible, universal cellular automata that follow rules modeling CPT reversibility - a symmetry principle drawn from fundamental physics.

  He also chaired the PDP-1 Restoration Project, which restored and reactivated the Computer History Museum's PDP-1 computer after seven months of work.

• 7. Digital Philosophy

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  Fredkin's most ambitious claim is that the universe is, in a precise technical sense, a computation. He called this view Digital Philosophy, and it belongs to a broader school of thought called pancomputationalism, which holds that all physical processes are forms of computation or information processing at the most fundamental level of reality.

  The view connects to older philosophical traditions. Pancomputationalism, as Fredkin developed it, relates to atomism, determinism, mechanism, monism, naturalism, philosophical realism, reductionism, and scientific empiricism. The claim is not merely a metaphor. Pancomputationalists argue that biology reduces to chemistry, chemistry reduces to physics, and physics reduces to the computation of information.

  Fredkin's version of this view has several specific commitments. Everything in physical reality must have a digital informational representation. All changes in physical nature follow from digital informational processes. Nature is finite and digital. He also argued that the traditional concept of the soul has a counterpart in what he called a static/dynamic soul, defined in terms of digital philosophy.

  He articulated these ideas across a series of papers: "Introduction to Digital Philosophy", "On the Soul", "Finite Nature", "A New Cosmogony", and "Digital Mechanics". A profile of Fredkin, along with a readable account of his theories, appeared in Robert Wright's 1988 book "Three Scientists and Their Gods". That section was excerpted in The Atlantic Monthly in April 1988. According to Wright, the character Stephen Falken in the film WarGames was modeled after Fredkin.