Douglas Bruce Lenat (September 13, 1950 – August 31, 2023) was an American
computer scientist
A computer scientist is a scientist who specializes in the academic study of computer science.
Computer scientists typically work on the theoretical side of computation. Although computer scientists can also focus their work and research on ...
and researcher in
artificial intelligence
Artificial intelligence (AI) is the capability of computer, computational systems to perform tasks typically associated with human intelligence, such as learning, reasoning, problem-solving, perception, and decision-making. It is a field of re ...
who was the founder and
CEO of
Cycorp, Inc. in
Austin, Texas
Austin ( ) is the List of capitals in the United States, capital city of the U.S. state of Texas. It is the county seat and most populous city of Travis County, Texas, Travis County, with portions extending into Hays County, Texas, Hays and W ...
.
Lenat was awarded the biannual
IJCAI Computers and Thought Award in 1976 for creating the machine-learning program
AM. He has worked on (symbolic, not statistical)
machine learning
Machine learning (ML) is a field of study in artificial intelligence concerned with the development and study of Computational statistics, statistical algorithms that can learn from data and generalise to unseen data, and thus perform Task ( ...
(with his AM and
Eurisko programs), knowledge representation,
"cognitive economy",
blackboard systems, and what he dubbed in 1984 "
ontological engineering"
(with his
Cyc program at
MCC and, since 1994, at
Cycorp). He has also worked in military simulations,
and numerous projects for the US government, military, intelligence, and scientific organizations. In 1980, he published a critique of conventional random-mutation Darwinism.
He authored a series of articles
in the
Journal of Artificial Intelligence exploring the nature of heuristic rules.
Lenat was one of the original Fellows of the
AAAI, and is the only individual to have served on the Scientific Advisory Boards of both Microsoft and Apple. He was a Fellow of the
AAAS, AAAI, and
Cognitive Science Society, and an editor of the
J. Automated Reasoning,
J. Learning Sciences, and
J. Applied Ontology. He was one of the founders of
TTI/Vanguard in 1991 and member of it
advisory board He was named one of the Wired 25.
Background and education
Lenat was born in
Philadelphia
Philadelphia ( ), colloquially referred to as Philly, is the List of municipalities in Pennsylvania, most populous city in the U.S. state of Pennsylvania and the List of United States cities by population, sixth-most populous city in the Unit ...
, United States, on September 13, 1950. When he was 5, the family moved to
Wilmington, Delaware
Wilmington is the List of municipalities in Delaware, most populous city in the U.S. state of Delaware. The city was built on the site of Fort Christina, the first Swedish colonization of the Americas, Swedish settlement in North America. It lie ...
, where his father, Nathan Lenat, owned a
bottling plant. His father died when he was 13 and the family then returned to Pennsylvania, where he attended
Cheltenham High School. His after-school job was cleaning rat cages and goose pens at
Beaver College which motivated him to learn programming as a better occupation.
He attended the
University of Pennsylvania
The University of Pennsylvania (Penn or UPenn) is a Private university, private Ivy League research university in Philadelphia, Pennsylvania, United States. One of nine colonial colleges, it was chartered in 1755 through the efforts of f ...
, supporting himself by programming, including the design and development of a
natural language interface for a
United States Navy
The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...
online
operations manual. He graduated with
bachelor's degree
A bachelor's degree (from Medieval Latin ''baccalaureus'') or baccalaureate (from Modern Latin ''baccalaureatus'') is an undergraduate degree awarded by colleges and universities upon completion of a course of study lasting three to six years ...
s in Mathematics and Physics, and a
master's degree
A master's degree (from Latin ) is a postgraduate academic degree awarded by universities or colleges upon completion of a course of study demonstrating mastery or a high-order overview of a specific field of study or area of professional prac ...
in Applied Mathematics, all in 1972.
Lenat was a Ph.D. student in Computer Science at Stanford University, where his published research included automatic
program synthesis
In computer science, program synthesis is the task to construct a computer program, program that provably correct, provably satisfies a given high-level formal specification. In contrast to program verification, the program is to be constructed rat ...
from input/output pairs and from natural language clarification dialogues.
Research
In 1976, Lenat received his
Ph.D. in Computer Science from
Stanford University
Leland Stanford Junior University, commonly referred to as Stanford University, is a Private university, private research university in Stanford, California, United States. It was founded in 1885 by railroad magnate Leland Stanford (the eighth ...
, "AM: Discovery in mathematics as heuristic search" sponsored by
ARPA.
[ DTIC Accession Number: ADA155378] It was republished as ''Knowledge-based systems in artificial intelligence'',
along with the Ph.D. thesis of Randall Davis, McGraw-Hill, 1982. His thesis advisor was Professor
Cordell Green.
His thesis,
AM (Automated Mathematician) was one of the first computer programs that attempted to make discoveries, i.e., to be a theorem ''proposer'' rather than a theorem ''prover''. Experimenting with the program fueled a cycle of criticism and improvement. Many issues had to be dealt with in constructing such a program: how to represent knowledge formally, expressively, and concretely, how to program hundreds of heuristic "interestingness" rules to judge the worth of new discoveries, heuristics for when to reason symbolically and inductively ''versus'' when to reason statistically from frequency data, what the architecture—the design constraints—of such reasoning programs might be, why heuristics work, and what their "inner structure" might be. AM was one of the first steps toward demonstrating that computer programs can make novel and creative discoveries.
In 1976, Lenat started teaching as an assistant professor of computer science at
Carnegie Mellon and commenced his work on the AI program
Eurisko. The limitation with AM was that it was locked into following a fixed set of interestingness heuristics; Eurisko, by contrast, represented its heuristic rules as first class objects and hence it could explore, manipulate, and discover new heuristics just as AM explored, manipulated, and discovered new domain concepts.
Lenat returned to Stanford as an assistant professor of computer science in 1978 and continued his research building the Eurisko automated discovery and heuristic-discovery program. Eurisko made many interesting discoveries and enjoyed significant acclaim, with Lenat's paper "Heuretics: Theoretical and Experimental Study of Heuristic Rules"
winning the Best Paper award at the 1982
AAAI conference.
A call for "common sense"
Lenat (working with John Seely Brown at Xerox PARC) published in 1984 an analysis of what were the limitations of his AM and Eurisko lines of research.
It concluded that progress toward real, general, symbolic AI would require a vast knowledge base of "common sense", suitably formalized and represented, and an inference engine capable of finding tens- or hundreds-deep conclusions and arguments that followed from the application of that knowledge base to specific questions and applications.
The successes, and analysis of the limitations, of this AM and Eurisko approach to AI, and the concluding plea for the massive (multi-thousand-person-year, decades-long) R&D effort would be required to break that bottleneck to AI, led to attention in 1982 from
Admiral Bob Inman and the then-forming
MCC research consortium in
Austin, Texas
Austin ( ) is the List of capitals in the United States, capital city of the U.S. state of Texas. It is the county seat and most populous city of Travis County, Texas, Travis County, with portions extending into Hays County, Texas, Hays and W ...
, culminating in Lenat's becoming principal scientist of MCC from 1984–1994, though he continued even after this period to return to Stanford to teach approximately one course per year. At the 400-person MCC, Lenat was able to have several dozen researchers work on that
common sense knowledge base, rather than just a few graduate students.
Cycorp
The fruits of the first decade of R&D on
Cyc were spun out of MCC into a company, Cycorp, at the end of 1994. In 1986, he estimated the effort to complete Cyc would be at least 250,000 rules and 1,000
person-years of effort,
probably twice that, and by 2017, he and his team had spent about 2,000 person-years of effort building Cyc, creating approximately 24 million rules and assertions (not counting "facts").
Lenat continued to work on Cyc as CEO of Cycorp until his death. While the first decade of work on Cyc (1984–1994) was funded by large American companies pooling long-term research funds to compete with the Japanese
Fifth Generation Computer Project, and the second decade (1995–2006) of work on Cyc was funded by US government agencies' research contracts, the third decade up through the present (2007–2023) has been largely supported through commercial applications of Cyc, including in the financial services, energy, and healthcare areas.
One of these later projects was a
learning by teaching application called Mathcraft.
Personal life and death
Lenat was married to Merle Baruch, with whom he had a daughter;
they divorced and he later married Cycorp business manager Mary Shepherd.
He died of
bile duct cancer on August 31, 2023, at the age of 72.
Quotes

* "Intelligence is ten million rules."
This refers to the prior and tacit knowledge that authors presume their readers all possess (such as "if person x knows person y, then x's date of death can't be earlier than y's date of birth") ''not counting the vastly larger number of "facts" such as one might find in Wikipedia or by Googling.''
* "The time may come when a greatly expanded Cyc will underlie countless software applications. But reaching that goal could easily take another two decades."
* "Once you have a truly massive amount of information integrated as knowledge, then the human-software system will be superhuman, in the same sense that mankind with writing is superhuman compared to mankind before writing."
* "Sometimes the ''veneer'' of intelligence is not enough."
* “If computers were human, they’d present themselves as autistic, schizophrenic, or otherwise brittle. It would be unwise or dangerous for that person to take care of children and cook meals, but it’s on the horizon for home robots. That’s like saying, ‘We have an important job to do, but we’re going to hire dogs and cats to do it.'”
* "What we needed, he says, is nothing less than an “AI
Manhattan Project
The Manhattan Project was a research and development program undertaken during World War II to produce the first nuclear weapons. It was led by the United States in collaboration with the United Kingdom and Canada.
From 1942 to 1946, the ...
”, a full frontal assault on common sense: the challenge is to create an
Encyclopédia of Common sense",
Michio Kaku
Michio Kaku (; ; born January 24, 1947) is an American theoretical physicist, Science communication, science communicator, futurologist, and writer of popular-science. He is a professor of theoretical physics at the City College of New York and ...
citing Lenat.
Writings
*
*
*
* Lenat, Douglas B. "Computer Software for Intelligent Systems: An Underview of AI," in ''Scientific American,'' September 1984.
* Lenat, Douglas B.; Clarkson, Albert; Kircmidjian, Garo (1983). "An Expert System for Indications & Warning Analysis". ''Proceedings of the Eighth International Joint Conference on Artificial Intelligence - Volume 1''. IJCAI'83. San Francisco, CA, USA: Morgan Kaufmann Publishers Inc.: 259–262.
* Lenat, Douglas B.; Feigenbaum, Edward A. (February 1991). "On the Thresholds of Knowledge". ''Artif. Intell''. 47 (1-3): 185–250. . .
* Lenat, Douglas B.; Guha, R. V. (1990-01-01). ''Building Large Knowledge-Based Systems: Representation and Inference in the Cyc Project''. Reading, Mass.: Addison-Wesley. .
* Lenat, Douglas B. ''From 2001 to 2001: Common Sense and the Mind of HAL''
* Lenat, Douglas B. (2008-07-10). "The Voice of the Turtle: Whatever Happened to AI?". ''AI Magazine''. 29(2).
doi:10.1609/aimag.v29i2.2106.
ISSN
An International Standard Serial Number (ISSN) is an eight-digit to uniquely identify a periodical publication (periodical), such as a magazine. The ISSN is especially helpful in distinguishing between serials with the same title. ISSNs a ...
0738-4602
* Blackstone E.H., Lenat, D.B. and Ishwaran H. ''Infrastructure required to learn which care is best: methods that need to be developed'', in (Olsen L., Grossman, C., and McGinnis, M., eds.) ''Learning What Works: Infrastructure Required for Comparative Effectiveness Research''. Institute of Medicine Learning Health System Series, The National Academies Press, pp. 123–144, 2011.
* Lenat DB, Durlach P. “Reinforcing Math Knowledge by Immersing Students in a Simulated Learning-By-Teaching Experience.” '' J. International Journal of Artificial Intelligence in Education.'', 2014
* Lenat, Douglas B. (2016-04-13). "WWTS (What Would Turing Say?)". ''AI Magazine''. 37 (1): 97–101.
doi:10.1609/aimag.v37i1.2644.
ISSN
An International Standard Serial Number (ISSN) is an eight-digit to uniquely identify a periodical publication (periodical), such as a magazine. The ISSN is especially helpful in distinguishing between serials with the same title. ISSNs a ...
0738-4602
* See also many of the References, below.
References
Further reading
*
External links
Douglas Lenat bio page at Cyc.com
"Beyond the Semantic Web" video lectureat
NIPS 2008.
"How David Beats Goliath" articleat The New Yorker.
"Douglas Lenat: Cyc and the Quest to Solve Common Sense Reasoning in AI."Lex Fridman Podcast #221, 2021.
{{DEFAULTSORT:Lenat, Douglas
1950 births
2023 deaths
Fellows of the Association for the Advancement of Artificial Intelligence
Fellows of the American Association for the Advancement of Science
American artificial intelligence researchers
Lisp (programming language) people
American computer businesspeople
Fellows of the Cognitive Science Society
Stanford University School of Engineering alumni
University of Pennsylvania alumni
Businesspeople from Philadelphia