Steps aside from conventional ideas about diagrams to examine how they work. Brings to bear ideas from a perceptual psychologist, a communication theorist, and a philosopher. Introduces the papers in this special issue as diagrams for worldmaking. (SR)

Reconsiders the usual typologies of diagram presentations, questioning accepted taxonomies. Examines diagrammatic structures, revealing some hardened categories. Suggests that new discoveries can be made if questions are raised about how information is framed. (SR)