  We conclude this section by noting again that Mally developed the first formal logical system of deontic logic, in Mally 1926. This system is described and analyzed in some detail in the entry  Mally’s deontic logic.  This entry explains how Mally introduced an operator (!) to form statements of the form ‘It ought to be the case that A’ (‘!A’), and how the logical axioms of his system implied the following, problematic claim: