[T]he titles noted down were those which had aroused Warburg’s scholarly curios-ity while he was engaged on a piece of research. They were all interconnected in apersonal way as the bibliographical sum total of his own activity. These lists were,therefore, his guide as a librarian ; not that he consulted them every time he readbooksellers’ and publishers’ catalogues ; they had become part of his system and schol-arly existence. [...] Often one saw Warburg standing tired and distressed bent over hisboxes with a packet of index cards, trying to ind for each one the best place withinthe system ; it looked like a waste of energy. [...] It took some time to realise that hisaim was not bibliographical. This was his method of deining the limits and contentsof his scholarly world and the experience gained here became decisive in selectingbooks for the Library. 5