Types, Tableaus and Gödel’s God in Isabelle/HOL

David Fuenmayor 📧 and Christoph Benzmüller 🌐

May 1, 2017

This is a development version of this entry. It might change over time and is not stable. Please refer to release versions for citations.


A computer-formalisation of the essential parts of Fitting's textbook "Types, Tableaus and Gödel's God" in Isabelle/HOL is presented. In particular, Fitting's (and Anderson's) variant of the ontological argument is verified and confirmed. This variant avoids the modal collapse, which has been criticised as an undesirable side-effect of Kurt Gödel's (and Dana Scott's) versions of the ontological argument. Fitting's work is employing an intensional higher-order modal logic, which we shallowly embed here in classical higher-order logic. We then utilize the embedded logic for the formalisation of Fitting's argument. (See also the earlier AFP entry “Gödel's God in Isabelle/HOL”.)


BSD License


Session Types_Tableaus_and_Goedels_God