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Lines of Thought

Branching Diagrams and the Medieval Mind

We think with objects—we conduct our lives surrounded by external devices that help us recall information, calculate, plan, design, make decisions, articulate ideas, and organize the chaos that fills our heads. Medieval scholars learned to think with their pages in a peculiar way: drawing hundreds of tree diagrams. Lines of Thought is the first book to investigate this prevalent but poorly studied notational habit, analyzing the practice from linguistic and cognitive perspectives and studying its application across theology, philosophy, law, and medicine.

These diagrams not only allow a glimpse into the thinking practices of the past but also constitute a chapter in the history of how people learned to rely on external devices—from stone to parchment to slide rules to smartphones—for recording, storing, and processing information. Beautifully illustrated throughout with previously unstudied and unedited diagrams, Lines of Thought is a historical overview of an important cognitive habit, providing a new window into the world of medieval scholars and their patterns of thinking.

272 pages | 4 color plates, 27 halftones, 86 line drawings, 3 tables | 8-1/4 x 11 | © 2021

History: History of Ideas

History of Science

Literature and Literary Criticism: General Criticism and Critical Theory

Medieval Studies


“[Even-Ezra] parses the parsing of long-gone readers with depth and relish, emerging from the thicket with a judicious and companionable discussion of HTs and their ramifications (pun essential) for our understanding of how reading, thinking, pen work, and the book medium may be inextricably entwined . . . . From cover to close, the argument of the book is fused with its design. Should an engaged reader annotate their copy with words, lines, or schemata, they would actively extend the lively subject of this welcome work.” 

Modern Philology

"This handsome, well-informed study of a seemingly esoteric subject, horizontal tree diagrams that populate the margins of medieval manuscripts and sometimes whole folios, should prove illuminating to all medievalists, as it offers insight not only into the conceptual processes of the age, but also into medieval readers' engagement with texts. . . . The erudite subject matter is conveyed in a clear and lively style sprinkled with personal remarks, and illustrated with numerous reproductions of HTs in both Latin and translated, plus beautiful manuscript photos in black and white and color. . . . Recommended."


“Offers a rich, transdisciplinary study, both broad and precise, qualitative and quantitative, of [horizontal tree] diagrams. . . . This book will be of great value to any medieval historian interested in the history of ideas and cultural practices, and will undoubtedly constitute a reference work in this field, while at the same time opening up new avenues for research.” 


“A thought‑provoking and stimulating book to read and an elegant publication to explore. . . . [the] monograph succeeds in raising awareness and stimulating interest in the understudied topic of the use of branching diagrams on scholastic texts.”

Comptes rendus de l'Académie des Sciences

"[Lines of Thought] is a triumph of the printer’s art and typography. . . There can be no doubt that Ayelet Even-Ezra has made an important contribution to our understanding of medieval scholasticism and academic culture in this
thought-provoking volume, which will spur discussion and further studies."

The Vatican Library Review

“A provocative account of the medieval use of branching, dichotomous diagrams with important implications for our understanding of the medieval mind and its processes of cognition. . . . The book is intricately crafted and delightfully illustrated throughout with Even-Ezra’s own branching diagrams, demonstrating their power, versatility, and appeal to the modern as much as medieval mind.” 

Renaissance Quarterly

“Remember the story of Thamus, that sceptical Egyptian god who predicted that young minds would be ruined by writing? The branching diagram, in Even-Ezra’s account, represents one good outcome of the invention of writing. These diagrams could facilitate deeper reflection, especially of an abstract kind, during sessions of intensive reading. They could also be aids to memory, rather than its substitutes, because they repackaged information in formal patterns that could stick in the mind. Medieval note-takers filled the margins of medieval books with these diagrams, and many are evidence of careful attention and a desire to crystalize new knowledge. Even-Ezra describes how the rise of these diagrams—a new kind of writing technology—reshaped cognition.”


"Even-Ezra's study is an excitingly original contribution to the histories of cognitive psychology and information design that explores the question of how people were thinking, not just what they thought. Focusing on the logical horizontal tree diagrams that are ubiquitous in the margins of European medieval university manuscripts and early printed books, she demonstrates with much detailed evidence how these diagrams—too often dismissed by historians as mere ‘doodling’ by bored beginners—functioned as a primary means for medieval scholars to visually comprehend their learning. A compelling example of the Extended Mind Theory now prominent in modern neuropsychology, this book will be of interest not only to medieval historians, art historians, and scholars of the book, but to anyone with an interest in information design and associative learning practices."

Mary Carruthers, New York University

"Even-Ezra roots the history of ideas in her probing analysis of habits of reading materialized in the horizontal tree diagrams that fill the margins of medieval university manuscripts. Lines of Thought places the relationship between spatialized patterns of visualization and scholastic thought, famously formulated by Erwin Panofsky, on an entirely new footing. Applying concepts from linguistics and cognitive science within a framework inspired by Extended Mind Theory, the author reconstructs coordinated habits of hand and mind that remain as critical today in literary criticism, cognitive studies, and computational linguistics as they were to medieval theology, philosophy, literature, logic, law, and medicine. A brilliant and utterly original book."

Jeffrey F. Hamburger, author of Diagramming Devotion: Berthold of Nuremberg’s Transformation of Hrabanus Maurus’s Poems in Praise of the Cross

Table of Contents


Part I

1 The Form: Chronological, Linguistic, and Cognitive Perspectives
1.1 Form: A Chronological Perspective
1.2 Form: A Linguistic Perspective
1.3 Form: A Cognitive Perspective

2 The Habit: On What, Where, Who, When, and How Often
2.1 Diagramming as a Form of Marginal Annotation
2.2 Parasitic, Embedded, and Tapestry Forms
2.3 Beyond the Classroom: French and Hebrew
2.4 Conclusion

Part II

3 Structures of Concepts: Distinctions
3.1 Natural Philosophy, Metaphysics, Ethics 
3.2 Biblical Distinctions
3.3 Canon and Civil Law 
3.4 Medicine
3.5 Conclusion

4 Structures of Language
4.1 Verse and Rhyme
4.2 Letter Writing (Ars Dictaminis)
4.3 Grammar

5 Structure of Texts
5.1 Orientation and Composition: Theological Questions
5.2 Analysis: Argument
5.3 Analysis: Biblical Narrative
5.4 What HT Diagramming Tells Us about the Scholastic Perception of Texts: Authors as Architects, Texts as Wisely Made Constructions 
5.5 Coda: Back to the Future—Parallels to the Divisio Textus in Twentieth-Century Narrative Analyses

Appendix: Latin and English Surface Text of the Book of Job Parsed and Numbered (Translation Follows the English Standard Version)


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