John Pollock, a founding father of the area of defeasible argumentation, has died. He combined theoretical, computational and practical considerations in his design of an ‘artificial person’, OSCAR (see, e.g., his Cognitive carpentry). In this high ambition, he has had no followers.
See, e.g., his influential paper Defeasible reasoning (in Cognitive Science, 11:481–518, 1987; also available in full text). A – too brief – one page introduction to his influential ideas on undercutting and rebutting defeaters is in this text (p. 229) on that other founding father of defeasible argumentation Stephen Toulmin.