What makes the Farolfi ledger a key document in European history – indeed, world history – is that this wreck of a notebook is the first place where we see all the abstract concepts of accountancy, and the practical techniques by which they were managed, used at once. For all their sophistication, earlier civilisations – Greeks, Arabs, Chinese – ha

The Romans solved one of the medium’s problems, finding a way to protect the writing on a wax tablet, making it suitable for legal documents or contracts. They drilled holes through its frame, tied it shut with a cord, and applied wax seals – up to seven, depending on the seriousness of the document.

The last paragraph of ‘The Extended Mind’ anticipated this, noting that the ‘reconception of ourselves’ that the hypothesis demanded would have ‘significant consequences’, not least moral and ethical implications. ‘In some cases,’ it said, ‘interfering with someone’s environment will have the same moral significance as interfering with their person

But we can easily picture a world in which there are very few such things. What objects in the everyday life of an early medieval peasant allowed them to extend their minds? The parish Bible, a measuring stick or string, perhaps; the counting board in a shop, a dice game, a sundial. With such limited opportunities, it’s no surprise that this enviro

What would traditionally be seen as property crime may instead count as a crime of violence. And it helps to explain the strange strength of the bonds that we form with our notebooks and diaries if we understand them to be extensions of our minds, parts of our belief and cognitive systems that happen to reside outside our skulls but are otherwise i

The Dutch prospered, and their neighbours, over time, followed their lead. Today, just as every corporation works out its balance sheet and profit and loss according to rules devised in Florence in the thirteenth century, every capitalist country is, in theory at least, run along similar rational, well-organised lines.

In another major step, the ledger defined an accounting period, turning twelve months into one financial year. Yet another was the concept of algebraic opposition – the relationship between assets and liabilities which Manucci reconciled with his careful credit and debit entries.

‘What this would mean is,’ Pennebaker concludes, ‘if I have more working memory, I should do better on exams: and people do. If I have better working memory, I should interact more with my friends, and listen to you when you’re telling me about your problems, and be more present. In a sense, my mind is clearer, I should sleep better – and people do

Islamic cities boasted million-volume libraries and streets of booksellers: administrators, students, teachers, and thinkers of all kinds relied on relatively cheap, plentiful paper to do their work.