Arguing from Definition to Verbal Classification: The Case of Redefining 'Planet' to Exclude Pluto

Douglas Walton


The recent redefinition of 'planet' that excludes Pluto as a planet led to controversy that provides a case study of how competing scientific definitions can be supported by characteristic types of evidence. An argumentation scheme from Hastings is used to analyze argument from verbal classification as a form of inference used in rational argumentation. The Toulmin-style format is compared to more recently developed ways of modeling such cases that stem from advances in argumentation technology in artificial intelligence. Using
these tools, it is shown how argumentation schemes, in particular
argument from verbal classification and argument from definition to verbal classification, apply to cases of scientific argumentation.


scientific definition; classification; decisions about definitions; competing definitions; argumentation schemes; arguments based on classifications; defeasible ontologies; artificial intelligence

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ISSN: 0824-2577