Llull’s Art was famously obscure even to its contemporaries

Evidence

The key to providing the rational argumentation for these confrontations is Llull’s Art. The Art, an arcane matrix of interwoven concepts, presented in a complex system of geometrical figures and tree diagrams, has daunted and discouraged many of Llull’s readers from the thirteenth century to the present. Llull himself was aware of this problem, to which he responded by simplifying and streamlining his system and by creating mnemonic devices to help the reader memorize it. — John V. Tolan, Saracens, 1301

Categorization

• XREF: Llull’s Art with its tree diagrams recalls the chart-theoretic knowledge machines later built by Leibniz and medieval memory systems described by Frances Yates.