This is the original I.J. Good paper from 1965 — the one that introduced the phrase "intelligence explosion" into the technical lexicon. Six decades before Bostrom, before Yudkowsky, before every AI safety essay of the 2020s, a British statistician and former Bletchley Park cryptanalyst who worked alongside Alan Turing sketched the entire recursive self-improvement argument in a few crisp pages.

The famous passage is worth reading in its original form:

"Let an ultraintelligent machine be defined as a machine that can far surpass all the intellectual activities of any man however clever. Since the design of machines is one of these intellectual activities, an ultraintelligent machine could design even better machines; there would then unquestionably be an 'intelligence explosion,' and the intelligence of man would be left far behind. Thus the first ultraintelligent machine is the last invention that man need ever make."

Why this deserves attention from a technical audience in 2026:

• Primary source discipline. Most engineers have only encountered this argument through third- and fourth-hand summaries. Reading Good directly reveals how much of modern AI risk discourse is a restatement (or dilution) of a 60-year-old argument, and how much has genuinely advanced.
• Historical texture. Good was writing in an era when "machine intelligence" mostly meant chess programs and pattern classifiers. His willingness to reason past that horizon — to ask what happens after parity — is a masterclass in taking speculative technical arguments seriously without getting lost in them.
• Surprising nuance. The paper isn't just the intelligence-explosion soundbite. Good spends real time on subgoal formation, the economics of building such a machine, information-theoretic bounds on learning, and the ethical apparatus needed. Some of it reads as remarkably contemporary; some of it reads as a period piece — and the gap between the two is instructive.
• Context for current debates. When people argue whether current LLM scaling curves imply an intelligence explosion, they are arguing about a hypothesis Good formalized in 1965. Knowing what he actually claimed — and what he assumed — sharpens the argument.

Hosted on Mark Liberman's Language Log page at Penn, it's a clean PDF scan of the original chapter from Advances in Computers, Vol. 6. Thirty minutes of reading; a much longer half-life in your thinking.