 Łukasiewicz was interested in intuitionistic logic, not least because, like his own, it rejected the law of excluded middle. In a late article published in 1952, he gave an elegant axiomatization with ten axioms, using the letters \(F\), \(T\) and \(O\) for the intuitionist connectives of implication, conjunction and disjunction respectively, in order to obviate clashes caused by “competition” for the connectives, though interestingly he kept the usual negation for both systems. He then showed how to define classical implication as \(NTpNq\), formulated this definition using a variable functor as the implication