Ayelet Even-Ezra's Lines of Thought offers 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. Since the classic work of Walter Ong, the use of such diagrams has been universally associated with Ramism and the early modern quantification of thought. While there has been a growing awareness of the presence of such diagrams in Renaissance and humanist contexts, Even-Ezra's monograph is the first to directly challenge Ong's paradigm. After reading her work, there can be no doubt of the prevalence, and indeed sheer ubiquity, of branching diagrams in medieval manuscripts, nor of their presence across the entire range of disciplines. 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.
The first part of the work is devoted to discussion of the form of these branching diagrams. Drawing on the work of Mary Carruthers and others on medieval diagrams, but departing from their mnemonic and teaching focus, Even-Ezra seeks to place branching diagrams within the broader history of cognition. Applying extended-mind theory, her focus is on branching diagrams as an externalization of mental processes. Such an approach also resonates with Pierre Bourdieu's influential theory of habitus, and Even-Ezra is keen to reveal branching diagrams as a neglected habit of medieval learning. Significantly, Even-Ezra sharply distinguishes branching diagrams from a rich array of other medieval visualization techniques, focusing exclusively on horizontal tree diagrams and not the more well-known vertical tree diagrams, such as the Porphyrian Tree or the Lullist Tree of Sciences.
Such a distinction is not merely stylistic but serves to reinforce the connection that branching diagrams have to linear patterns of speech. For, as Even-Ezra exhaustively demonstrates, one of their key uses was to show the structural relationship and sequencing of lines of text, revealing their inner logic. This also allowed the permutation of sentence clauses, providing an easy means of generating new patterns of argument or even redrafting entire texts. Such an interpretation is further confirmed by the fact that the vast majority of such diagrams are to be found as rough marginal glosses in manuscripts: an important clue to their neglect by scholarship. Branching diagrams thus reveal important modes of composition previously hidden to us by the final, polished form of a manuscript.
The second part of the work offers an in-depth view of branching diagrams across a whole array of disciplines. Key here is their use in structuring scholastic distinctiones, and branching diagrams unsurprisingly proved an important tool for theologians commenting on Peter Lombard's Sentences. Similar examples can be found in the analysis of biblical exegesis, where the ability to make subtle distinctions was also fundamental to the entire enterprise. As Even-Ezra insightfully points out, precisely the same skills were often deployed in analyzing the texts of Aristotle and other authorities, and partly for this reason branching diagrams appear commonly in works of logic, physics, metaphysics, law, and medicine. Their intimate connection to patterns of speech also made them indispensable in the analysis of prose and poetry.
For Even-Ezra, branching diagrams are therefore an important expression of a shared mode of thought continuing throughout the medieval centuries. As she concludes, they reveal the author as architect and the text itself as a complex, hierarchically ordered construction branching out into multiple dimensions. In this sense, Erwin Panofksy was absolutely right to recognize the intimate connection between the Gothic cathedral and the vast summae of theology constructed in the thirteenth century. Of course, to properly substantiate such a claim will require rather more evidence. For, while clearly revealing the role of branching diagrams as mental habits, Even-Ezra has much less to say about their ontology or their connection to the encyclopedic tendency of the medieval mind. Nevertheless, as a pioneering work revealing the cognitive richness and sophistication of branching diagrams, Lines of Thought is an enormously valuable work, mapping out the medieval mind in fresh and exciting ways and hinting at deep and unexpected connections with the methodological turn of Renaissance thought.
