John L. Pollock
Encyclopedia
John L. Pollock was an American philosopher known for influential work in epistemology, philosophical logic
, cognitive science
, and artificial intelligence
.
Born John Leslie Pollock in Atchison Kansas, January 28, 1940, Pollock earned a triple-major physics, mathematics, and philosophy degree at the University of Minnesota in 1961. In 1965, his doctoral dissertation Analyticity and Implication at UC Berkeley was advised by Ernest Adams (making Pollock an intellectual descendant of Gottfried Leibniz
and Immanuel Kant
, through Ernest Nagel
and Patrick Suppes
). This dissertation contained an appendix on defeasible reasoning
that would eventually blossom into his main contribution to philosophy.
Pollock took faculty positions at SUNY Buffalo, University of Rochester
, University of Michigan
, and University of Arizona
. At Arizona, he helped found the Cognitive Science
Program.
of contemporary philosophers. It appeared at a time when American philosophy, and especially American epistemology, was obsessed with criteria and the analysis
of what does it mean to know?. The Gettier problem
, for example, was one of the most popular problems of the day: why is it that knowledge is not exactly "justified, true belief"? Pollock's book steps back from analytic criteria, which are presumably necessary and sufficient conditions
. His epistemic norms are governed by defeasible reasoning; they are ceteris paribus
conditions that can admit exceptions. Several other epistemologists (notably at Brown University
, such as Ernest Sosa
, Keith Lehrer
, John Ladd, and especially Roderick Chisholm
) had written about defeasibility and epistemology. But Pollock's book, which combined a broad scope and a crucial innovation, brought the ideas into the philosophical mainstream.
, 1987, though his non-syntactic ideas were almost fully mature in Knowledge and Justification. Pollock traced the history of his own thinking (e.g., in a footnote in Pollock and Cruz, Contemporary Theories of Knowledge, 1999, p. 36, note 37, and elsewhere) to his first paper on epistemology, "Criteria and our knowledge of the material world," Philosophical Review 76, 1967. He thought that Roderick Chisholm
had influenced his thinking on the subject, but he also said he was attempting to interpret Ludwig Wittgenstein
directly, and sometimes credited Stephen Toulmin
on the subject of argument. Although his work had considerable impact in the area of Artificial intelligence and law
, Pollock was not himself interested much in jurisprudence
or theories of legal reasoning, and he never acknowledged the inheritance of defeasible reasoning through H.L.A. Hart. Pollock also held informal logic
ians and scholars of rhetoric
at a distance, though defeasible reasoning has natural affinities in argument (logic).
Pollock's "undercutting defeat" and "rebutting defeat" are now fixtures in the defeasible reasoning literature. He later added "self-defeat" and other kinds of defeat mechanisms, but the original distinction remains the most popular.
Although aided by a strong tail wind from AI and a few contemporary like minded philosophers (e.g., Donald Nute, Nicholas Asher, Bob Causey), it is certain that defeasible reasoning went from the obscure to the mainstream in philosophy because of John Pollock, in the short time between the publication of Knowledge and Justification and the second edition of Contemporary Theories of Knowledge.
-based program that had an "interest-based" reasoner. Pollock claimed that the efficiency of his theorem-prover was based on its unwillingness to draw "uninteresting" conclusions. Although OSCAR did not benefit from the contributions of a large number of professional programmers, it must be compared to CyC, Soar (cognitive architecture)
, and Novamente
for its inventor's ambition.
Pollock described Oscar's main features as the ability to reason defeasibly about perception,
change and persistence, causation, probabilities, plan construction and evaluation, and decision.
OSCAR grew out of the Prologemena on How to Build a Person, which colleagues must have assumed was a facetious use of personhood at the time. However, Pollock's own attitude toward OSCAR was more machinating: he looked forward to future cognitive taxonomies that would classify OSCAR generously as a legitimate anthropomorphic form.
s.
Philosophical logic
Philosophical logic is a term introduced by Bertrand Russell to represent his idea that the workings of natural language and thought can only be adequately represented by an artificial language; essentially it was his formalization program for the natural language...
, cognitive science
Cognitive science
Cognitive science is the interdisciplinary scientific study of mind and its processes. It examines what cognition is, what it does and how it works. It includes research on how information is processed , represented, and transformed in behaviour, nervous system or machine...
, and artificial intelligence
Artificial intelligence
Artificial intelligence is the intelligence of machines and the branch of computer science that aims to create it. AI textbooks define the field as "the study and design of intelligent agents" where an intelligent agent is a system that perceives its environment and takes actions that maximize its...
.
Born John Leslie Pollock in Atchison Kansas, January 28, 1940, Pollock earned a triple-major physics, mathematics, and philosophy degree at the University of Minnesota in 1961. In 1965, his doctoral dissertation Analyticity and Implication at UC Berkeley was advised by Ernest Adams (making Pollock an intellectual descendant of Gottfried Leibniz
Gottfried Leibniz
Gottfried Wilhelm Leibniz was a German philosopher and mathematician. He wrote in different languages, primarily in Latin , French and German ....
and Immanuel Kant
Immanuel Kant
Immanuel Kant was a German philosopher from Königsberg , researching, lecturing and writing on philosophy and anthropology at the end of the 18th Century Enlightenment....
, through Ernest Nagel
Ernest Nagel
Ernest Nagel was a Czech-American philosopher of science. Along with Rudolf Carnap, Hans Reichenbach, and Carl Hempel, he is sometimes seen as one of the major figures of the logical positivist movement....
and Patrick Suppes
Patrick Suppes
Patrick Colonel Suppes is an American philosopher who has made significant contributions to philosophy of science, the theory of measurement, the foundations of quantum mechanics, decision theory, psychology, and educational technology...
). This dissertation contained an appendix on defeasible reasoning
Defeasible reasoning
Defeasible reasoning is a kind of reasoning that is based on reasons that are defeasible, as opposed to the indefeasible reasons of deductive logic...
that would eventually blossom into his main contribution to philosophy.
Pollock took faculty positions at SUNY Buffalo, University of Rochester
University of Rochester
The University of Rochester is a private, nonsectarian, research university in Rochester, New York, United States. The university grants undergraduate and graduate degrees, including doctoral and professional degrees. The university has six schools and various interdisciplinary programs.The...
, University of Michigan
University of Michigan
The University of Michigan is a public research university located in Ann Arbor, Michigan in the United States. It is the state's oldest university and the flagship campus of the University of Michigan...
, and University of Arizona
University of Arizona
The University of Arizona is a land-grant and space-grant public institution of higher education and research located in Tucson, Arizona, United States. The University of Arizona was the first university in the state of Arizona, founded in 1885...
. At Arizona, he helped found the Cognitive Science
Cognitive science
Cognitive science is the interdisciplinary scientific study of mind and its processes. It examines what cognition is, what it does and how it works. It includes research on how information is processed , represented, and transformed in behaviour, nervous system or machine...
Program.
Knowledge and Justification
Knowledge and Justification, or simply KJ as it is known to at least two generations of philosophy graduate students, is the book that put John Pollock on the A-listA-list
A-list is a term that alludes to major movie stars, or the most bankable in the Hollywood film industry.The A-list is part of a larger guide called The Hot List that has become an industry-standard guide in Hollywood...
of contemporary philosophers. It appeared at a time when American philosophy, and especially American epistemology, was obsessed with criteria and the analysis
Analysis
Analysis is the process of breaking a complex topic or substance into smaller parts to gain a better understanding of it. The technique has been applied in the study of mathematics and logic since before Aristotle , though analysis as a formal concept is a relatively recent development.The word is...
of what does it mean to know?. The Gettier problem
Gettier problem
A Gettier problem is a problem in modern epistemology issuing from counter-examples to the definition of knowledge as justified true belief . The problem owes its name to a three-page paper published in 1963, by Edmund Gettier, called "Is Justified True Belief Knowledge?", in which Gettier argues...
, for example, was one of the most popular problems of the day: why is it that knowledge is not exactly "justified, true belief"? Pollock's book steps back from analytic criteria, which are presumably necessary and sufficient conditions
Necessary and sufficient conditions
In logic, the words necessity and sufficiency refer to the implicational relationships between statements. The assertion that one statement is a necessary and sufficient condition of another means that the former statement is true if and only if the latter is true.-Definitions:A necessary condition...
. His epistemic norms are governed by defeasible reasoning; they are ceteris paribus
Ceteris paribus
or is a Latin phrase, literally translated as "with other things the same," or "all other things being equal or held constant." It is an example of an ablative absolute and is commonly rendered in English as "all other things being equal." A prediction, or a statement about causal or logical...
conditions that can admit exceptions. Several other epistemologists (notably at Brown University
Brown University
Brown University is a private, Ivy League university located in Providence, Rhode Island, United States. Founded in 1764 prior to American independence from the British Empire as the College in the English Colony of Rhode Island and Providence Plantations early in the reign of King George III ,...
, such as Ernest Sosa
Ernest Sosa
Ernest Sosa is an American philosopher primarily interested in epistemology. He is currently Board of Governors Professor of Philosophy at Rutgers University. He has been at Rutgers full-time since January, 2007; previously, he had been at Brown University since 1964...
, Keith Lehrer
Keith Lehrer
Keith Lehrer is the Regent's Professor emeritus of Philosophy at the University of Arizona with an affiliation with the University of Miami in Florida. He previously taught at the University of Rochester....
, John Ladd, and especially Roderick Chisholm
Roderick Chisholm
Roderick M. Chisholm was an American philosopher known for his work on epistemology, metaphysics, free will, and the philosophy of perception. He received his Ph.D. at Harvard University under Clarence Irving Lewis and Donald C. Williams, and taught at Brown University...
) had written about defeasibility and epistemology. But Pollock's book, which combined a broad scope and a crucial innovation, brought the ideas into the philosophical mainstream.
Defeasible Reasoning
Pollock became known as "Mr. Defeasible Reasoning" among philosophers in the two decades before his death. In Artificial intelligence, where non-monotonic reasoning had caused intellectual upheaval, scholars sympathetic to Pollock's work held him in great esteem for his early commitment and clarity. Pollock's most direct pronouncement is the paper "Defeasible reasoning" in Cognitive ScienceCognitive science
Cognitive science is the interdisciplinary scientific study of mind and its processes. It examines what cognition is, what it does and how it works. It includes research on how information is processed , represented, and transformed in behaviour, nervous system or machine...
, 1987, though his non-syntactic ideas were almost fully mature in Knowledge and Justification. Pollock traced the history of his own thinking (e.g., in a footnote in Pollock and Cruz, Contemporary Theories of Knowledge, 1999, p. 36, note 37, and elsewhere) to his first paper on epistemology, "Criteria and our knowledge of the material world," Philosophical Review 76, 1967. He thought that Roderick Chisholm
Roderick Chisholm
Roderick M. Chisholm was an American philosopher known for his work on epistemology, metaphysics, free will, and the philosophy of perception. He received his Ph.D. at Harvard University under Clarence Irving Lewis and Donald C. Williams, and taught at Brown University...
had influenced his thinking on the subject, but he also said he was attempting to interpret Ludwig Wittgenstein
Ludwig Wittgenstein
Ludwig Josef Johann Wittgenstein was an Austrian philosopher who worked primarily in logic, the philosophy of mathematics, the philosophy of mind, and the philosophy of language. He was professor in philosophy at the University of Cambridge from 1939 until 1947...
directly, and sometimes credited Stephen Toulmin
Stephen Toulmin
Stephen Edelston Toulmin was a British philosopher, author, and educator. Influenced by Ludwig Wittgenstein, Toulmin devoted his works to the analysis of moral reasoning. Throughout his writings, he sought to develop practical arguments which can be used effectively in evaluating the ethics behind...
on the subject of argument. Although his work had considerable impact in the area of Artificial intelligence and law
Artificial intelligence and law
Artificial intelligence and Law is a subfield of artificial intelligence mainly concerned with applications of AI to legal informatics problems and original research on those problems...
, Pollock was not himself interested much in jurisprudence
Jurisprudence
Jurisprudence is the theory and philosophy of law. Scholars of jurisprudence, or legal theorists , hope to obtain a deeper understanding of the nature of law, of legal reasoning, legal systems and of legal institutions...
or theories of legal reasoning, and he never acknowledged the inheritance of defeasible reasoning through H.L.A. Hart. Pollock also held informal logic
Informal logic
Informal logic, intuitively, refers to the principles of logic and logical thought outside of a formal setting. However, perhaps because of the informal in the title, the precise definition of informal logic is matters of some dispute. Ralph H. Johnson and J...
ians and scholars of rhetoric
Rhetoric
Rhetoric is the art of discourse, an art that aims to improve the facility of speakers or writers who attempt to inform, persuade, or motivate particular audiences in specific situations. As a subject of formal study and a productive civic practice, rhetoric has played a central role in the Western...
at a distance, though defeasible reasoning has natural affinities in argument (logic).
Pollock's "undercutting defeat" and "rebutting defeat" are now fixtures in the defeasible reasoning literature. He later added "self-defeat" and other kinds of defeat mechanisms, but the original distinction remains the most popular.
Although aided by a strong tail wind from AI and a few contemporary like minded philosophers (e.g., Donald Nute, Nicholas Asher, Bob Causey), it is certain that defeasible reasoning went from the obscure to the mainstream in philosophy because of John Pollock, in the short time between the publication of Knowledge and Justification and the second edition of Contemporary Theories of Knowledge.
OSCAR / How to Build a Person
Pollock devoted considerable time later in his career to a software project called OSCAR, an artificial intelligence software prototype he called an "artilect". OSCAR was largely an implementation of Pollock's ideas on defeasible reasoning, but it also embodied his less well known and often unpublished ideas about intentions, interests, strategies for problem solving, and other cognitive architectural design. OSCAR was a LISPLisp
A lisp is a speech impediment, historically also known as sigmatism. Stereotypically, people with a lisp are unable to pronounce sibilants , and replace them with interdentals , though there are actually several kinds of lisp...
-based program that had an "interest-based" reasoner. Pollock claimed that the efficiency of his theorem-prover was based on its unwillingness to draw "uninteresting" conclusions. Although OSCAR did not benefit from the contributions of a large number of professional programmers, it must be compared to CyC, Soar (cognitive architecture)
Soar (cognitive architecture)
Soar is a symbolic cognitive architecture, created by John Laird, Allen Newell, and Paul Rosenbloom at Carnegie Mellon University, now maintained by John Laird's research group at the University of Michigan. It is both a view of what cognition is and an implementation of that view through a...
, and Novamente
Ben Goertzel
Ben Goertzel , is an American author and researcher in the field of artificial intelligence. He currently leads Novamente LLC, a privately held software company that attempts to develop a form of strong AI, which he calls "Artificial General Intelligence"...
for its inventor's ambition.
Pollock described Oscar's main features as the ability to reason defeasibly about perception,
change and persistence, causation, probabilities, plan construction and evaluation, and decision.
OSCAR grew out of the Prologemena on How to Build a Person, which colleagues must have assumed was a facetious use of personhood at the time. However, Pollock's own attitude toward OSCAR was more machinating: he looked forward to future cognitive taxonomies that would classify OSCAR generously as a legitimate anthropomorphic form.
Nomic Probability
Nomic Probability and the Foundations of Induction, Oxford, 1990 was Pollock's deep investigation of the relationship between defeasible reasoning and the estimation of probability from frequencies (direct inference of probability). It is a maturation of ideas originally found in a 1983 Theory and Decision paper. This work must be compared to Henry E. Kyburg's theories of probability, although Pollock believed that he was theorizing about a broader variety of statistical inferenceStatistical inference
In statistics, statistical inference is the process of drawing conclusions from data that are subject to random variation, for example, observational errors or sampling variation...
s.
Books
- Introduction to Symbolic Logic, Holt Rinehart Winston, 1969.
- Knowledge and Justification, Princeton, 1974.
- Subjunctive Reasoning, Springer, 1976.
- Language and Thought, Princeton, 1982.
- The Foundations of Philosophical Semantics, Princeton, 1984.
- Contemporary Theories of Knowledge, first edition, Rowman-Littlefield, 1987.
- How to Build a Person: A prolegomenon, MIT Press, 1989.
- Technical Methods in Philosophy, Westview, 1990.
- Nomic Probability and The Foundations of Induction, Oxford, 1990.
- Philosophy and AI: Essays at the Interface, with R. Cummins, MIT Press, 1995.
- Cognitive Carpentry: A blueprint for how to build a person, MIT Press, 1995.
- Contemporary Theories of Knowledge, with J. Cruz, second edition, Rowman-Littlefield, 1999.
- Thinking about Acting: Logical Foundations for Rational Decision Making, Oxford, 2006.
Important Papers
- "Criteria and our knowledge of the material world," The Philosophical Review, 1967.
- "Basic modal logic," Journal of Symbolic Logic, 1967.
- "What Is an Epistemological Problem? American Philosophical Quarterly, 1968.
- "The structure of epistemic justification," American Philosophical Quarterly, 1970.
- "Perceptual knowledge," The Philosophical Review, 1971.
- "The logic of projectibility," Philosophy of Science, 1972.
- "Subjunctive generalizations," Synthese, 1974.
- "Four Kinds of Conditionals," American Philosophical Quarterly, 1975.
- "The 'possible worlds' analysis of counterfactuals," Philosophical Studies, 1976.
- "Thinking about an Object," Midwest Studies in Philosophy, 1980.
- "A refined theory of counterfactuals," Journal of Philosophical Logic, 1981.
- "Epistemology and probability," Synthese, 1983.
- "How Do You Maximize Expectation Value?" Nous, 1983.
- "A theory of direct inference," Theory and Decision, 1983.
- "A solution to the problem of induction," Nous, 1984.
- "Reliability and justified belief," Canadian Journal of Philosophy, 1984.
- "A theory of moral reasoning," Ethics, 1986.
- "The Paradox of the Preface," Philosophy of Science, 1986.
- "Epistemic norms," Synthese, 1987.
- "Defeasible reasoning," Cognitive Science, 1987.
- "How To Build a Person: The Physical Basis for Mentality," Philosophical Perspectives, 1987.
- "My brother, the machine," Nous, 1988.
- "OSCAR: A general theory of rationality," Journal of Experimental and Theoretical Artificial Intelligence, 1989.
- "Interest driven suppositional reasoning," Journal of Automated Reasoning, 1990.
- "Self-defeating arguments," Minds and Machines, 1991.
- "A theory of defeasible reasoning," International Journal of Intelligent Systems, 1991.
- "New foundations for practical reasoning," Minds and Machines, 1992.
- "How to reason defeasibly," Artificial Intelligence, 1992.
- "The theory of nomic probability," Synthese, 1992.
- "The phylogeny of rationality," Cognitive Science, 1993.
- "Foundations for direct inference," Theory and Decision, 1994.
- "Justification and defeat," Artificial Intelligence, 1994.
- "The projectibility constraint," in Grue! The New Riddle of Induction, ed. Douglas Stalker, Open Court, 1994.
- "Implementing defeasible reasoning," Workshop on Computational Dialectics - FAPR, 1996.
- "Oscar - A general-purpose defeasible reasoner," Journal of Applied Nonclassical Logics, 1996.
- "Taking perception seriously," Proceedings of the first international conference on Autonomous Agents, 1997.
- "Reasoning about change and persistence: A solution to the frame problem," Nous, 1997.
- "The logical foundations of goal-regression planning in autonomous agents," Artificial Intelligence, 1998.
- "Perceiving and reasoning about a changing world," Computational Intelligence, 1998.
- "Procedural Epistemology," in The Digital Phoenix: How Computers are Changing Philosophy, Bynum and Moor, eds., Wiley, 1998.
- "Planning Agents," in Foundations of Rational Agency, ed. Rao and Wooldridge, Kluwer, 1999.
- "Belief revision and epistemology," with AS Gillies, Synthese, 2000.
- "Rational cognition in OSCAR," Lecture notes in computer science, 2000.
- "Defeasible reasoning with variable degrees of justification," Artificial Intelligence, 2001.
- "Causal probability," Synthese, 2002.
- "The logical foundations of means-end reasoning," Common Sense, Reasoning, & Rationality, 2002.
- "Rational choice and action omnipotence," The Philosophical Review, 2002.
- "Plans and decisions," Theory and Decision, 2004.
- "What Am I? Virtual machines and the mind/body problem," Philosophy and Phenomenological Research, 2008.