The law was framed by Cambridge University Professor John Edensor Littlewood and published in a 1986 collection of his work, A Mathematician's Miscellany. It seeks, among other things, to debunk one element of supposed supernatural phenomenology and is related to the more general law of truly large numbers, which states that with a sample size large enough, any outrageous (in terms of probability model of single sample) thing is likely to happen.

Littlewood defines a miracle as an exceptional event of special significance occurring at one in-a-million frequency. He assumes that during the hours a human is awake and alert, a human will see or hear one "event" per second, which may be either exceptional or unexceptional. Additionally, Littlewood supposes that a human is alert for about eight hours daily.

As a result, in 35 days, a human will have experienced about one million events under these suppositions. Therefore, accepting this definition of a miracle, one can expect to observe one miraculous event every 35 days, on average – therefore, according to this reasoning, seemingly miraculous events are commonplace.

• Littlewood's Law described in a review of Debunked! ESP, Telekinesis, Other Pseudoscience by Freeman Dyson, in The New York Review of Books (subscription required)