From Robert Anton Wilson's Cosmic Trigger

In the early ’60s in Tangier, William S. Burroughs knew a certain Captain Clark who ran a ferry from Tangier to Spain. One day, Clark said to Burroughs that he’d been running the ferry 23 years without an accident. That very day, the ferry sank, killing Clark and everybody aboard. In the evening, Burroughs was thinking about this when he turned on the radio. The first newscast told about the crash of an Eastern Airlines plane on the New York - Miami route. The pilot was another Captain Clark and the flight was listed as Flight 23.

(Aha! Now you understand the line, “Captain Clark welcomes you aboard,” which appears, always with sinister overtones, in various of Burroughs’ surrealistic novels.)

Burroughs began keeping records of odd coincidences. To his astonishment, 23s appeared in a lot of them. When he told me about this, I began keeping my own records - and 23s appeared in many of them. (Readers of Koestler’s Challenge of Chance will find that there are a great many 23s in that encyclopedia of odd coincidences also.) This, of course, illustrates Jano Watts’ concept of “The Net” - the lines of coincidence-synchronicity that connect everything-with-everything. It is also an analogy (and maybe more than an analogy) with what physicists call QUIP - the Quantum Inseparability Principle. QUIP, which is accepted by some and denied by other physicists, holds that every particle does affect every other particle, everywhere.

A plausible extension is given by Dr. Fritjof Capra, a young Berkley physicist who experienced quantum inseparability during an altered state of consciousness. In The Tao of Physics, Dr. Capra defends the “Bootstrap Theory,” which holds, in effect, that everything is the cause of everything, every which way in time.”

Quantum inseparability and the Bootstrap Theory are differing ontological flavors of what are called "non-local" models in modern physics. Non-local models are not limited by Einstein's speed-of-light barrier; they allow, for instance, that the future may determine the present as much as the past does, as in the famous limerick, 

  There was a young lady named Bright
       Whose speed was much faster than light;
       She departed one day
In a relative way
And returned on the previous night.

The latest convert to the non-local or non-chronological model is the famous astronomer-cosmologist Sir Fred Hoyle, who explicitly advocates a non-local trans-time theory of causality in his latest book, Ten Faces of the Universe. Non-local theories, like Jung's synchronicity, take us out of the Newtonian action-reaction machine and bring us eerily close to the logic of I Ching and Taoism, in which the seemingly random tossing of three coins may reveal an archetypal pattern of both personal and cosmological significance.

With that kind of rationale (or rationalization) I accepted the 23 enigma as a signal that I should attempt to decipher. After a while my passion for jotting down every significant 23 that came my way began to annoy my Beautiful Red-Headed Wife, Arlen. "It's all in your mind," she told me on several occasions. "You're just noticing the 23s and ignoring other numbers." Of course. But she was annoyed by being implicated in the 23 mystery even before she met me. Our two oldest daughters (by her previous marriage) were born on February 23 and August 23 respectively.

Once the Numerologist went to see the Academy Award film, Charly, with a friend who was particularly dubious about this 23 obsession. The story of the film concerns a low-grade moron (IQ around 70) who is transformed by neuro-surgery into a superhuman genius (IQ 200+). In the crucial operation scene, the number on the operating room is visible, and it is, of course, 23. The friend sat bolt upright. 

"Jesus H. Particular Christ," the friend said hollowly, "How do you do it?"

Most of the 23 data were incorporated into Illuminatus, to which the reader is referred. Here are a few examples: "Mad Dog" Coll was shot on 23rd Street when he was 23 years old; a year later, Dutch Schultz (who paid for the Coll assassination) was himself fatally shot on October 23, 1935. Marty Krompier, king of the Harlem numbers racket, was non-fatally shot on the same October 23, 1935. ("It's got to be one of them coincidences," he told police.) Schultz's killer, Charlie Workman, served 23 years of a life sentence and was then paroled.

When the donkey metaprogrammer has noticed a few oddities of this sort, the key signal becomes prominent everywhere. I soon noticed the 23 axioms that open Euclid's Geometry; the fact that the mad bomber in the film, Airport, has seat 23; that in the old stage productions of A Tale of Two Cities, Sydney Carton is the 23rd man guillotined in the gory climax (some lexicographers believe this is the origin of the inscrutable slang expression "23 Skiddoo!"); 23, in telegra-pher's code, means "bust" or "break the line," while Hexagram 23 in the / Ching means "Break Apart." I was even thrilled by noting that in conception Mom and Dad each contribute 23 chromosomes to the fertilized egg, while within the DNA coil of genetic metaprogramming instructions there are unexplained bonding irregularities every 23rd angstrom. 

Aleister Crowley's Cabalistic Dictionary later excited weird speculations about 23 perhaps being somehow involved with reproduction by defining 23 as the number of "parting, removal, separation," "joy," "a thread," and "life."

Run the following, from Professor Hans Seisel of the University of Chicago, through your most skeptical filter: My grandparents on my mother's side lived in Gablonz, Mozartstrasse 23; we lived in Vienna at Rossaurelaende 23; our law office at Gonzagasse 23; my mother at Alserstrasse 23, tuer (apart-ment) 23, and so it went...

Professor Seisel's mother, while visiting Monte Carlo, purchased a book, Ilya Ehrenburg's Die Liebe der Jeannie Ney, in which the heroine wins a great deal betting on number 23 at roulette. She decided to experiment; 23 came up on the second try. This is archetypical. We shall see, as we advance, that the peculiar entities in charge of Dr. John Lilly's hypothetical Cosmic Coincidence Control Center pay special attention to those who pay attention to them. 

Meanwhile the Numerologist had a new rationalization for his obsession: the famous story of how Dr. James Watson, coming down a spiral staircase at Oxford, suddenly flashed intuitively on the spiral shape of the DNA. All the micro-photographic evidence at that time seemed to contradict his theory, but Watson irrationally trusted his intuition and kept working on that model. Eventually he won the Nobel Prize for proving that the DNA is a double helix (two spirals interwoven). 23 was my spiral staircase, my intuitive signal.