On Classifying Abduction

We can witness the recent surge of interest in classifying different patterns or types of abduction. Many philosophers, including Thagard, Magnani, Gabbay and Woods, Schurz, and Hoffmann, have suggested their own classifications emphasizing different aspects of abduction (Thagard 1988; Magnani 2001, 2009; Gabbay and Woods 2005; Schurz 2008; Hoffmann 2011). Such a development is remarkable, in view of the fact that until quite recently the focus of the research on Peircean abduction was basically to identify its logical form (Kapitan 1997). In one sense, it is strange that after all these years abduction is still unfamiliar to the general public: not on a par with deduction and induction. In another sense, however, it is also remarkable that abduction has been extensively studied by artificial intelligence researchers, cognitive scientists, and semioticians as well as by philosophers of science. No doubt, the diverse attempts in classifying abduction must represent the fact that the current level of the study of abduction is pretty high. It is Schurz (2008) that could be a nice point of departure for useful comparisons of all these classifications, for he provides us with a rather extensive list of different “patterns of abduction”. In terms of what entity is to be abduced, he distinguished between more than ten different patterns of abduction, grouped under 4 categories: i.e., factual abduction, law-abduction, theoretical model abduction, and second-order existential abduction. One significant point in Schurz’s classification is that he emphasizes the importance of second-order existential abduction, paying special attention on common cause abduction. Largely concurring with Schurz, Hoffmann further expands the list into a table by adding what he calls “meta-diagrammatic abduction” as a fifth category (Hoffmann 2011, 581). Unlike Schurz, however, Hoffmann highlights what he calls “theoretical-model abduction” as a precondition for any abduction (Hoffmann 2011, 580). Schurz’s and Hoffmann’s classifications of abduction basically concern its “explanatory” character. They do not consider the problem of non-explanatory abduction, which is instead illustrated by Gabbay and