Image copyright Oxford University

Scribbles, notes and drawings from the personal library of John Stuart Mill shed new light on one of Britain's great philosophers, say researchers.

A team from Somerville College, Oxford, has scoured Mill's private library of nearly 1,700 volumes.

Cataloguing the comments and symbols he made on the edges of books and pamphlets helps build a picture of the way his thinking developed, they say.

Mill, also an MP and economist, is best known for his essay, On Liberty.

He wrote in defence of the ethical theory of utilitarianism - the idea that actions are good if they benefit a majority of people - and has been described as the most influential English-speaking philosopher of the 19th Century.

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"Having access to Mill's unvarnished reactions to his reading is as close as we will ever get to witnessing one of history's foremost minds in the process of thinking," said Dr Albert Pionke, a Victorian specialist from the University of Alabama, who is leading the research.

One of the most striking sources in the collection is Mill's boyhood copy of Franco Burgersdijk's Institutionum Logicarum, a work of Aristotelian philosophy used as a textbook by university students well into the 18th Century.

Image copyright Oxford University Image caption Mill's extensive library collection

Mill was educated at home by his father, James, himself a philosopher and close friend of another highly influential figure in philosophy, Jeremy Bentham.

The boy's copy is small, three by four inches, designed to fit into an overcoat pocket. It's in Latin, a language he had learned by the age of eight, along with Greek.

In the margins are 500 numbers in the boy's handwriting. Dr Pionke believes this is a running index that Mill, then aged 12, had created, to help him answer his father's searching questions - an indication of his "pressure-filled childhood".

"It's a meaty little book, 600 pages of dense text, all in Latin. It clearly took immense amounts of work."

There are also a handful of more childish-looking doodles, including a triangle and a fan-shaped squiggle - suggesting perhaps that even this brilliant child scholar had moments of distraction.

The Somerville collection includes works by Mill's contemporaries, who were also sometimes friends.

Image copyright Oxford University Image caption A handwritten note in de Tocqueville's book

There is a copy of the influential, Democracy in America, by the French political scientist Alexis de Tocqueville, who inscribed volumes three and four - published in 1840 - "in friendship" to "John Mill".

At the end of a chapter entitled, Some Reflections on American manners, Mill commented, in a handwritten note: "How is it possible for one confessedly ignorant of England to say what is, and what is not, really American in their manners?"

De Tocqueville and Mill were close: Mill had enormous respect for his friend's ideas. According to Dr Pionke, many will be surprised at the tone of the handwritten commentary.

The project is ambitious, cataloguing all the marginalia on a searchable website. Researchers have logged close to 10,000 marks so far and expect to find five times as many once they've been through the entire collection.

Image copyright Oxford University Image caption Musical notes are among Mill's many doodles

All the scrawls, doodles and drawings will be online.

So far, the team have identified 104 types, most of them familiar, like brackets or asterisks, others harder to decode, like a doodle resembling women's bloomers.

As their work continues, they hope to establish what each one means.