As a secretary of the Academy, Trendelenburg was charged with honoring Leibniz’s memory. Leibniz had been the first president of the “Societät der Wissenschaften” at Berlin, the predecessor institution of the Royal Prussian Academy of Science, founded on his initiative in 1700. In 1856, Trendelenburg delivered a seminal lecture entitled “Über Leibnizens Entwurf einer allgemeinen Charakteristik” at the Leibniz ceremony of the Academy at Berlin (Trendelenburg 1857). This paper was reprinted in the third volume of his Historische Beiträge zur Philosophie (1867). In this discussion of Leibniz, Trendelenburg stressed the essential role of signs in communication and reasoning. There is no logical relation between sign and intuition, but science has provided the opportunity to “bring the composition of the signs into immediate contact with contents of the concept” (Trendelenburg 1857, 3). The composition of the sign presents the characteristic marks distinguished and comprehended in the concept (ibid.). Trendelenburg called such a script “Begriffsschrift”. Maybe he took over this term from Wilhelm von Humboldt who had introduced it in 1824 (v. Humboldt 1826, quoted 1848, 532; cf. Thiel 1995, 20). According to Trendelenburg the beginnings of a Begriffsschrift were made, e.g., in the decimal number system. Trendelenburg saw the objectives of Leibniz’s program as widening such an approach to the complete domain of objects, thereby aiming at a “characteristic language of concepts” and a “general language of matter.” He mentioned the different names used by Leibniz: lingua characterica universalis (in fact Trendelenburg’s term; Leibniz used characteristica universalis), alphabet of human thoughts, calculus philosophicus, calculus ratiocinator, spécieuse générale. These names underline the significance Leibniz ascribed to this program for his philosophy. According to Trendelenburg, Leibniz aimed at “an adequate and therefore general signification of the essence [of conceptual content], namely by such analysis into the elements of concepts, that it becomes possible to treat it by calculation” (ibid., 6). He mentioned as historical precursors the ars magna of Raymundus Lullus and other conceptions of universal languages. Because of its generality, Leibniz’s characteristica universalis stands out compared with competing proposals by George Dalgarno (1661) and John Wilkins (1668), which were obtained from “choice, nature and chance,” and relied upon existing languages (ibid., 14–15).