 Besides his own early interest in logic and classical and ancient languages, the value of attention to language was familiar to Neurath from the Austrian fin-de-siècle culture of critique of language (Janik and Toulmin 1973), his interest (and his first wife’s) in literature, especially in Goethe (Zemplen 2006, see above), the internationalist and utopianists efforts at introducing new universal languages such as Volapük and Esperanto, the emphasis on signs and universal languages – to be known as pasigraphy – in the scholastic and rationalist philosophical traditions, in the traditions of empirical taxonomies and in the interest in universal language as instrument of knowledge and social order in the Enlightenment, a semiotic tradition in scientific epistemology including Helmholtz, Mach, Duhem and Peirce (Cat 2019) and the sociologist Ferdinand Tönnies’s formal approach to sociology and social signs (Tönnies 1899–1900 and Cartwright et al. 1996, 121–24). The significance of the internationalist and philosophical projects of pasigraphy were acknowledged also by Carnap. More “scientific” sources were recent technical developments in logic, philosophy of science and the foundation of mathematics often claiming Leibniz as a precursor (Leibniz’s logic and project of a universal characteristic had become widely recognized by the late nineteenth century (Peckhaus 2012)). Leading figures in such developments were Frege, Hilbert, Whitehead, Russell and Wittgenstein.