Paul Thagard

Paul R. Thagard
Born	Saskatchewan, Canada
Era	20th-century philosophy
Region	Western Philosophy
School	Analytic
Main interests	Philosophy of mind Cognitive science Philosophy of science Epistemology
Notable ideas	Multi-level interacting mechanisms

Paul Thagard is a Canadian philosopher who has published in many fields, including philosophy, cognitive science, and the philosophy of science. Thagard is currently a professor of Philosophy at the University of Waterloo, with cross appointment to Psychology and Computer Science. He is the director of the Cognitive Science Program. img http://en.wikipedia.org/wiki/File:Paul_Thagard.gif

Thagard is well cited for his work on the use of cognitive science in explaining conceptual revolutions in the history of science.

Biography

He is a graduate of the Universities of Saskatchewan, Cambridge, Toronto (Ph.D. in philosophy, 1977) and Michigan (M.S. in computer science, 1985). He was Chair of the Governing Board of the Cognitive Science Society [1], 1998–1999, and President of the Society for Machines and Mentality [2], 1997-1998. He has held a Canada Council Killam fellowship, and in 1999 was elected a fellow of the Royal Society of Canada. In 2003, he received a University of Waterloo Award for Excellence in Research, and in 2005 he was named a University Research Chair.

Coherence

Paul Thagard has proposed that many cognitive functions, including perception, analogy, explanation, decision-making, planning etc., can be understood as a form of (maximum) coherence computation.

Thagard (together with Karsten Verbeurgt) put forth a particular formalization of the concept of coherence as a constraint satisfaction problem. The model posits that coherence operates over a set of representational elements (e.g., propositions, images, etc.) which can either fit together (cohere) or resist fitting together (incohere).

If two elements p and q cohere they are connected by a positive constraint $(p,q)\in C^{+}$, and if two elements $p$ and $q$ incohere they are connected by a negative constraint $(p,q)\in C^{-}$. Furthermore, constraints are weighted, i.e., for each constraint $(p,q)\in C^{+}\cup C^{-}$ there is a positive weight $w(p,q)$.

According to Thagard, coherence maximization involves the partitioning of elements into accepted ($A$) and rejected ($R$) elements in such a way that maximum number (or maximum weight) of constraints is satisfied. Here a positive constraint $(p,q)$ is said to be satisfied if either both $p$ and $q$ are accepted ($p,q\in A$) or both $p$ and $q$ are rejected ($p,q\in R$). A negative constraint $(p,q)$ is satisfied if one element is accepted(say $p\in A$), and the other rejected ($q\in R$).

Philosophy of science

There has been some decrease in interest in the demarcation problem in recent years. Part of the problem is that many suspect that it is an intractable problem, since so many previous attempts have come up short. For example, many obvious examples of pseudoscience have been shown to be falsifiable, or verifiable, or revisable. Therefore many of the previously proposed demarcation criteria have not been judged as particularly reliable.

Thagard has proposed another set of principles to try to overcome these difficulties. According to Thagard's method, a theory is not scientific if:

1. It has been less progressive than alternative theories over a long period of time, and faces many unsolved problems; but
2. The community of practitioners makes little attempt to develop the theory towards solutions of the problems, shows no concern for attempts to evaluate the theory in relation to others, and is selective in considering confirmations and disconfirmations.

Major Works

Thagard is the author of:

• "The Brain and the Meaning of Life" Princeton University Press, 2010 ISBN 978-1-4008-3461-7
• Hot Thought: Mechanisms and Applications of Emotional Cognition (MIT Press, August, 2006, ISBN 0-262-20164-X)
• Coherence in Thought and Action (Bradford Book, 2000, ISBN 0-262-20131-3)
• How Scientists Explain Disease (Princeton University Press, 1999, ISBN 0-691-00261-4)
• Mind: An Introduction to Cognitive Science (MIT Press, 1996; second edition, 2005, ISBN 0-262-20154-2)(Trad. esp.: La mente, Buenos Aires/Madrid, Katz editores S.A, 2008, ISBN 9788496859210)
• Conceptual Revolutions (Princeton University Press, 1992, ISBN 0-691-02490-1)
• Computational Philosophy of Science (MIT Press, 1988, Bardford Book, 1993, ISBN 0-262-70048-4)

And co-author of:

• Mental Leaps: Analogy in Creative Thought (MIT Press, 1995, ISBN 0-262-08233-0)
• Induction: Processes of Inference, Learning, and Discovery (MIT Press, 1986, Bardford Book, 1989, ISBN 0-262-58096-9)

He is also editor of:

• Philosophy of Psychology and Cognitive Science (North-Holland, 2006, ISBN 0-444-51540-2).

• Thagard, P. and Verbeurgt, K. (1998). Coherence as constraint satisfaction. Cognitive Science, 22: 1-24.
• Thagard, P. (2000). Coherence in Thought and Action. MIT Press.

Many of Thagard's coherence articles are available online at http://cogsci.uwaterloo.ca/Articles/Pages/Coherence.html