The Ascribed Coherence of Thagard and Weick

This chapter continues our exploration of complexity, emergence, and in particular coherence. We begin with definitions. Coherence has a common meaning, “a sticking or cleaving together; union of parts of the same body; cohesion” (Webster’s Dictionary) and in philosophy it has acquired a fairly specific meaning, “the maximum satisfaction of constraints” (Thagard, 2000). The specific philosophical meaning comes from Paul Thagard, who intended:

…. to make contributions to philosophy, psychology, and computer science. The notion of coherence has been widely used in philosophy, particularly in ethics and epistemology, but has been left completely vague. In contrast, we present a characterization of coherence which is mathematically precise … [we] provide an abstract formal characterization that unifies numerous psychological theories. We provide a new mathematical framework that encompasses constraint satisfaction theories of hypothesis evaluation, analogical mapping, discourse comprehension, impression formation, and so on. Previously, these theories shared an informal characterization of cognition as parallel constraint satisfaction, along with use of connectionist algorithms to perform constraint satisfaction. Our new precise account of coherence makes clear what these theories have in common besides connectionist implementations. (Thagard, 2000)