Paul Thagard

Biography Thagard was born in Yorkton, Saskatchewan on September 28, 1950. He is a graduate of the Universities of Saskatchewan (B.A. in philosophy, 1971), Cambridge (M.A. in philosophy, 1973), 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 , 1998–1999, and President of the Society for Machines and Mentality , 1997–1998. In 2013 he won a Canada Council Killam Prize, 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.

Thagard was married to the psychologist Ziva Kunda. Kunda died in 2004.

Philosophical work Explanatory coherence Thagard has proposed that many cognitive functions—including perception, analogy, explanation, decision-making, and planning—can be modeled as coherence-based constraint satisfaction processes rather than as purely deductive or probabilistic reasoning.

Thagard (together with Karsten Verbeurgt) put forth a formalization of coherence as a constraint satisfaction problem. In this model, coherence operates over a set of representational elements (such as propositions or images) that may either fit together (cohere) or resist fitting together (incohere).

Pairs of elements are linked by either positive or negative constraints. If two elements and cohere, they are connected by a positive constraint ; if they incohere, they are connected by a negative constraint . Constraints are weighted, such that for each constraint there is an associated positive weight .

According to Thagard, coherence maximization involves partitioning elements into accepted and rejected sets so as to satisfy the maximum number, or maximum total weight, of constraints. A positive constraint is satisfied if both elements are accepted or both rejected . A negative constraint is satisfied if one element is accepted and the other rejected (for example, and ). This formulation treats reasoning as a global optimization process over interconnected representations rather than as a sequence of local logical inferences.

Philosophy of science Thagard worked on the demarcation problem in philosophy of science. Faced with the failure of verifiability and falsifiability, what he called "post positivist depression", he proposed in 1978 a criterion to define pseudoscience, with the broader goal being rescuing science from the relativism of Feyerabend and Rorty. According to Thagard's criterion, "A theory which purports to be scientific is pseudoscientific if and only if":

However, in 1988, Thagard wrote that this proposal should "be abandoned," because it had two flaws. Firstly it was hopeless to attempt to find necessary and sufficient conditions for pseudoscience in general, and secondly, the criterion was too soft on astrology which it was specifically meant to brand as pseudoscience.

Major works Thagard is the author/co-author of 17 books and over 200 articles. Dreams, Jokes, and Songs: How Brains Build Consciousness. (Oxford University Press, 2025). Falsehoods Fly: Why Misinformation Spreads and How to Stop it. (Columbia University Press, 2024). Balance: How it Works and What it Means. (Columbia University Press, 2022). Bots and Beasts: What Make Machines, Animals, and People Smart? (MIT Press, 2021). Brain-Mind: From Neurons to Consciousness and Creativity. (Oxford University Press, 2019). Mind-Society: From Brains to Social Sciences and Professions. (Oxford University Press, 2019).

The Cognitive Science of Science: Explanation, Discovery, and Conceptual Change. (MIT Press, 2012). The Brain and the Meaning of Life Princeton University Press, 2010 Hot Thought: Mechanisms and Applications of Emotional Cognition (MIT Press, August, 2006, ) Coherence in Thought and Action (MIT Press, 2000, ) How Scientists Explain Disease (Princeton University Press, 1999, ) Mind: An Introduction to Cognitive Science (MIT Press, 1996; second edition, 2005, )(Trad. esp.: La mente, Buenos Aires/Madrid, Katz editores S.A, 2008, ) Conceptual Revolutions (Princeton University Press, 1992, ) Computational Philosophy of Science (MIT Press, 1988, Bradford Books, 1993, )

And co-author of: Mental Leaps: Analogy in Creative Thought (MIT Press, 1995, ) Induction: Processes of Inference, Learning, and Discovery (MIT Press, 1986, Bradford Books, 1989, )

He is also editor of: Philosophy of Psychology and Cognitive Science (North-Holland, 2006, ).