Language as reason represents the unifying theme of this multifaceted reflection on Eddo Rigotti’s scientific contribution offered by his students and colleagues on the occasion of his seventieth birthday. Spanning argumentation theory, linguistics, psychology, semiotics and communication sciences, the volume reflects Rigotti’s generous personality and his trajectory of semiotician, philosopher, linguist and specialist in argumentation studies. Language as an instrument of communication with semiotic peculiarities is considered at different levels in which it manifests traces of reason at work. This means considering how reality reveals itself by means of language and how the semiotic character of language structures is used by people to enable joint actions and change the natural and social world. Particularly in focus is the realm of argumentation, that is of those joint actions where people exchange reasons in various communities, fora and markets in view of understanding and practical deliberation. To argumentation Eddo Rigotti devoted all his research efforts in recent years, with a keen sense of its intrinsic educational value and a sincere care for fostering the development of the argumentative mind.