\b[Not a <logical formula> of this language.] <Logical disjunction> is not one of its permitted <logical connectives>. Even though the displayed expression has an ordinary interpretation in a larger propositional language, membership in the specified <formal language> is a syntactic question. A logically equivalent <logical formula> using only <negation> and <logical implication> would have to be written with those symbols instead.

Solution

Past exam of the logic and set theory course of the University of Oxford / 2008 / A / 1 / c / b / Solution

 Solution (source code)