8.4 Some Properties of involving the Modal System K4

We now consider how to establish for the PITL operator the axiom “4” (PITL Theorem BfImpBfBf) found in the modal systems K4 and S4.

   DfDfEqvDf
   DfNotEqvNotBf
   DfDfNotEqvNotBfBf
   BfBfEqvBf
   BfImpBfBf

2023-09-12
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