ABSTRACT The four papers printed in this themed issue of the journal are on the general topic of seventeenth-century attempts to devise a philosophical language scheme or what was known as a ‘real character’. Each article approaches the topic from a distinctive perspective: two of the papers focus on the work of a single thinker; a third paper examines the technical notations being concurrently developed in the areas of mathematics, music, and chemistry; and the fourth explores the way such schemes rest on semi-submerged and controversial assumptions about the nature of speech and writing. What is common to the four papers is a consensus that, while previous work in this area has tended to focus primarily on a handful of the fully worked-out schemes, there are rich avenues yet to be fully exploited if the scope of research is re-oriented towards the study of notational systems in the context of their specific application. It is in this sense that we invite readers to view our topic as an open cross-roads of intersecting avenues for study, rather than as a closed market-place for the display and comparison of the models available.