 What Leibniz actually intended by his "characteristica universalis" and calculus ratiocinator, and the extent to which modern formal logic does justice to calculus, may never be established.Leibniz's idea of reasoning through a universal language of symbols and calculations remarkably foreshadows great 20th-century developments in formal systems, such as Turing completeness, where computation was used to define equivalent universal languages (see Turing degree).Leibniz has been noted as one of the most important logicians between the times of Aristotle and Gottlob Frege.