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December 2, 2015 @ 2:30 pm - 4:30 pm
A definition formulated correctly using necessary and sufficient conditions introduces new vocabulary via an interpretation in a familiar language. A recursive definition introduces the application of vocabulary to new objects in terms of previously understood applications to other, typically less complex, objects. A circular definition, such as the definition of truth that plagues our attempts to understand self-referential truth claims, may change the predicate that it defines. In this talk, I will reflect on a conception of definitions as dynamic operators. This includes the approach to relation-change dynamics introduced in  and studied algebraically in .
 P. Girard, J. Seligman and F. Liu. General dynamic dynamic logic. In S. Ghilardi T. Bolander and L. Moss, editors, Advances in Modal Logic, volume 9, pages 239–260. College Publications, 2012.
 M. Ma and J. Seligman. Algebraic semantics for dynamic dynamic logic. In W. van der Hoek, W. Holliday and W. Wang, editors, Logic and Rational Interaction (LORI 5), pages 255-267. Springer, 2015.