  Among the variant versions of Protothetic Leśniewski mentions in his 1929 article, one is a single-axiom version containing 82 signs. (In 1945 Sobociński produced a single axiom version with 54 signs only.) The other and more interesting idea is an algorithmic or “computative” system of Protothetic, mentioned above in Section 8. This is in effect a way to formalize the idea of truth-tables, but applied beyond truth-functions of sentences to more complex functors with arguments of first and higher order truth-functions. Leśniewski does not take the idea very far, but it was subsequently developed further by Owen Le Blanc (1991).