In 1848, Antonio Panizzi, Keeper of Printed Books for the British Museum, had a similar notion:By an alphabetical catalogue it is understood that the titles be entered in it under some “headings” alphabetically arranged. Now, inasmuch as in a large. library no one can know beforehand the j uxtaposition of these headings, and it would beimpossible to arrange them in the requisite order, if they cannot be easily shifted, each title is therefore written on separate “slips” of paper . . . which are frequently changed from one place to another as required. It is selfevident that if these “slips . . . be not uniform, both in size or substance, their arrangement will cause mechanical difficulties which take time and trouble to overcome.

Humanists had the tools and even the concepts to invent the cross-referenced thematic library catalogue, but they did not do so. We do not know why it took several hundred years and the Italian director of the British Museum, Antonio Panizzi, to create a truly modern reference catalogue through his “Ninety-One Cataloguing Rules” in 1841.