Carl Linnaeus Invented The Index Card

As a consequence of overseas discoveries, early modern scientists faced serious information overload. The sheer amount of exotic, hitherto unknown species reaching the shores of Europe forced naturalists to reconsider the ways in which information about the natural world was processed and organized.

The Swedish naturalist and physician Carl Linnaeus (1707-1778) – the father of modern taxonomy - has been described as a “pioneer of information retrieval”. But exactly how he was able to master such vast amounts of data has remained something of a mystery.

Staffan Mueller-Wille from the Centre for Medical History at the University of Exeter in the UK recently received a major grant from the Wellcome Trust to get to the bottom of Linnaeus’ method of data processing.

Speaking at the annual meeting of the British Society for the History of Science in Leicester, UK on Saturday 4 July, Mueller-Wille will reveal his preliminary findings of research on Linnaeus’ manuscripts held June 16 at the Linnaean Society of London.

Linnaeus had to manage a conflict between the need to bring information into a fixed order for purposes of later retrieval, and the need to permanently integrate new information into that order, says Mueller-Wille. “His solution to this dilemma was to keep information on particular subjects on separate sheets, which could be complemented and reshuffled,” he says.

Towards the end of his career, in the mid-1760s, Linnaeus took this further, inventing a paper tool that has since become very common: index cards. While stored in some fixed, conventional order, often alphabetically, index cards could be retrieved and shuffled around at will to update and compare information at any time.

“Although a seemingly mundane and simple innovation, Linnaeus' use of index cards marks a major shift in how eighteenth-century naturalists thought about the order of nature,” says Mueller-Wille. The natural world was no longer ordered on a fixed, linear scale, but came to be seen as a map-like natural system of multiple affinities.