John L. Pollock (1940–2009) was an American

philosopher Philosophy ('love of wisdom' in Ancient Greek) is a systematic study of general and fundamental questions concerning topics like existence, reason, knowledge, Value (ethics and social sciences), value, mind, and language. It is a rational an ...

known for influential work in

epistemology Epistemology is the branch of philosophy that examines the nature, origin, and limits of knowledge. Also called "the theory of knowledge", it explores different types of knowledge, such as propositional knowledge about facts, practical knowle ...

philosophical logic Understood in a narrow sense, philosophical logic is the area of logic that studies the application of logical methods to philosophical problems, often in the form of extended logical systems like modal logic. Some theorists conceive philosophic ...

cognitive science Cognitive science is the interdisciplinary, scientific study of the mind and its processes. It examines the nature, the tasks, and the functions of cognition (in a broad sense). Mental faculties of concern to cognitive scientists include percep ...

, and

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 ...

Life and career

Born John Leslie Pollock in Atchison, Kansas, on January 28, 1940, Pollock earned a triple-major

physics Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...

mathematics Mathematics is a field of study that discovers and organizes methods, Mathematical theory, theories and theorems that are developed and Mathematical proof, proved for the needs of empirical sciences and mathematics itself. There are many ar ...

, and

philosophy Philosophy ('love of wisdom' in Ancient Greek) is a systematic study of general and fundamental questions concerning topics like existence, reason, knowledge, Value (ethics and social sciences), value, mind, and language. It is a rational an ...

degree at the

University of Minnesota The University of Minnesota Twin Cities (historically known as University of Minnesota) is a public university, public Land-grant university, land-grant research university in the Minneapolis–Saint Paul, Twin Cities of Minneapolis and Saint ...

in 1961. In 1965, his doctoral dissertation ''Analyticity and Implication'' at the

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California), is a Public university, public Land-grant university, land-grant research university in Berkeley, California, United States. Founded in 1868 and named after t ...

was advised by Ernest Adams (making Pollock an intellectual descendant of

Gottfried Leibniz Gottfried Wilhelm Leibniz (or Leibnitz; – 14 November 1716) was a German polymath active as a mathematician, philosopher, scientist and diplomat who is credited, alongside Isaac Newton, Sir Isaac Newton, with the creation of calculus in ad ...

and

Immanuel Kant Immanuel Kant (born Emanuel Kant; 22 April 1724 – 12 February 1804) was a German Philosophy, philosopher and one of the central Age of Enlightenment, Enlightenment thinkers. Born in Königsberg, Kant's comprehensive and systematic works ...

, through

Ernest Nagel Ernest Nagel (; ; November 16, 1901 – September 20, 1985) was an American philosopher of science. Suppes, Patrick (1999)Biographical memoir of Ernest Nagel In '' American National Biograph''y (Vol. 16, pp. 216-218). New York: Oxford University ...

and

Patrick Suppes Patrick Colonel Suppes (; March 17, 1922 – November 17, 2014) was an American philosopher who made significant contributions to philosophy of science, the theory of measurement, the foundations of quantum mechanics, decision theory, psycholog ...

). This dissertation contained an appendix on

defeasible reasoning In philosophy of logic, defeasible reasoning is a kind of provisional reasoning that is rationally compelling, though not deductively valid. It usually occurs when a rule is given, but there may be specific exceptions to the rule, or subclasse ...

that would eventually blossom into his main contribution to philosophy. Pollock held faculty positions at SUNY Buffalo,

University of Rochester The University of Rochester is a private university, private research university in Rochester, New York, United States. It was founded in 1850 and moved into its current campus, next to the Genesee River in 1930. With approximately 30,000 full ...

University of Michigan The University of Michigan (U-M, U of M, or Michigan) is a public university, public research university in Ann Arbor, Michigan, United States. Founded in 1817, it is the oldest institution of higher education in the state. The University of Mi ...

, and

University of Arizona The University of Arizona (Arizona, U of A, UArizona, or UA) is a Public university, public Land-grant university, land-grant research university in Tucson, Arizona, United States. Founded in 1885 by the 13th Arizona Territorial Legislature, it ...

, where he spent most of his career. At Arizona, he helped found the

Cognitive Science Cognitive science is the interdisciplinary, scientific study of the mind and its processes. It examines the nature, the tasks, and the functions of cognition (in a broad sense). Mental faculties of concern to cognitive scientists include percep ...

Program. He was an avid mountain biker and founded a riding club in Southern Arizona.

Philosophical work

''Knowledge and Justification''

''Knowledge and Justification'' is the book that established Pollock in epistemology. It appeared at a time when American philosophy, and especially American epistemology, was obsessed with the

analysis Analysis (: analyses) is the process of breaking a complex topic or substance into smaller parts in order to gain a better understanding of it. The technique has been applied in the study of mathematics and logic since before Aristotle (38 ...

of what it means to ''know'' something. For instance, the '' Gettier problem'', one of the most frequently discussed problems of the day, asks why it is that holding a "justified true belief" that x is not equivalent to knowing that x. Pollock's book steps back from trying to identify the "analytic criteria" which might constitute the

necessary and sufficient conditions In logic and mathematics, necessity and sufficiency are terms used to describe a conditional or implicational relationship between two statements. For example, in the conditional statement: "If then ", is necessary for , because the truth of ...

for knowledge. His ''epistemic norms'' are governed by defeasible reasoning; they are ''

ceteris paribus ' (also spelled ') (Classical ) is a Latin phrase, meaning "other things equal"; some other English translations of the phrase are "all other things being equal", "other things held constant", "all else unchanged", and "all else being equal". ...

'' conditions that can admit exceptions. Several other epistemologists (notably at

Brown University Brown University is a Private university, private Ivy League research university in Providence, Rhode Island, United States. It is the List of colonial colleges, seventh-oldest institution of higher education in the US, founded in 1764 as the ' ...

, such as

Ernest Sosa Ernest Sosa (; ; born June 17, 1940) is an American philosopher primarily interested in epistemology. Since 2007 he has been Board of Governors Professor of Philosophy at Rutgers University, but he spent most of his career at Brown University. ...

, and especially

Roderick Chisholm Roderick Milton Chisholm ( ; November 27, 1916 – January 19, 1999) was an American philosopher known for his work on epistemology, metaphysics, free will, value theory, deontology, deontic logic and the philosophy of perception. Richard and ...

), as well as his Arizona colleague Keith Lehrer, 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

, 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

, 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

had influenced his thinking on the subject, but he also said he was attempting to interpret

Ludwig Wittgenstein Ludwig Josef Johann Wittgenstein ( ; ; 26 April 1889 – 29 April 1951) was an Austrian philosopher who worked primarily in logic, the philosophy of mathematics, the philosophy of mind, and the philosophy of language. From 1929 to 1947, Witt ...

directly, and sometimes credited

Stephen Toulmin Stephen Edelston Toulmin (; 25 March 1922 – 4 December 2009) 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 ...

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 Jurisprudence, also known as theory of law or philosophy of law, is the examination in a general perspective of what law is and what it ought to be. It investigates issues such as the definition of law; legal validity; legal norms and values ...

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 encompasses the principles of logic and logical thought outside of a formal setting (characterized by the usage of particular statements). However, the precise definition of "informal logic" is a matter of some dispute. Ralph H. ...

ians and scholars of

rhetoric Rhetoric is the art of persuasion. It is one of the three ancient arts of discourse ( trivium) along with grammar and logic/ dialectic. As an academic discipline within the humanities, rhetoric aims to study the techniques that speakers or w ...

at a distance, though defeasible reasoning has natural affinities in

argument An argument is a series of sentences, statements, or propositions some of which are called premises and one is the conclusion. The purpose of an argument is to give reasons for one's conclusion via justification, explanation, and/or persu ...

. 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

LISP Lisp (historically LISP, an abbreviation of "list processing") is a family of programming languages with a long history and a distinctive, fully parenthesized Polish notation#Explanation, prefix notation. Originally specified in the late 1950s, ...

-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 Cyc (pronounced ) is a long-term artificial intelligence (AI) project that aims to assemble a comprehensive ontology and knowledge base that spans the basic concepts and rules about how the world works. Hoping to capture common sense knowledge ...

Soar (cognitive architecture) Soar is a cognitive architecture, originally created by John Laird, Allen Newell, and Paul Rosenbloom at Carnegie Mellon University. The goal of the Soar project is to develop the fixed computational building blocks necessary for general intel ...

, 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. He described the evolution of Oscar in the Fable of Oscar in his book. OSCAR grew out of the Prologemena on ''How to Build a Person'', which colleagues must have assumed was a facetious use of ''

personhood Personhood is the status of being a person. Defining personhood is a controversial topic in philosophy and law and is closely tied with legal and political concepts of citizenship, equality, and liberty. According to law, only a legal person (ei ...

'' 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 Probability is a branch of mathematics and statistics concerning events and numerical descriptions of how likely they are to occur. The probability of an event is a number between 0 and 1; the larger the probability, the more likely an e ...

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 inference Statistical inference is the process of using data analysis to infer properties of an underlying probability distribution.Upton, G., Cook, I. (2008) ''Oxford Dictionary of Statistics'', OUP. . Inferential statistical analysis infers properties of ...

Publications

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.

Selected 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 The ''Journal of Experimental and Theoretical Artificial Intelligence'' is a quarterly peer-reviewed scientific journal published by Taylor and Francis. It covers all aspects of artificial intelligence and was established in 1989. The editor-in-chi ...

'', 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. * "Proving the non-existence of God," ''Inquiry : An Interdisciplinary Journal of Philosophy'', 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.

References

External links