Paul Thagard

Canadian philosopher (born 1950)
In the philosophy of mind, he is known for his attempts to apply connectionist models of coherence to theories of human thought and action. He is also known for HOTCO ("hot coherence"), which was his attempt to create a computer model of cognition that incorporated emotions at a fundamental level. In his general approach to philosophy, Thagard is sharply critical of analytic philosophy for being overly dependent upon intuitions as a source of evidence.

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.

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 , and if two elements and incohere they are connected by a negative constraint Furthermore, constraints are weighted, i. e., for each constraint there is a positive weight
According to Thagard, coherence maximization involves the partitioning of elements into accepted and rejected elements in such a way that maximum number (or maximum weight) of constraints is satisfied. Here a positive constraint is said to be satisfied if either both and are accepted or both and are rejected A negative constraint is satisfied if one element is accepted (say ), and the other rejected .

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":It has been less progressive than alternative theories over a long period of time, and faces many unsolved problems; but
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. 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.