Thomas Jefferson had one. Milton had one. Darwin had one. But why?
What is a commonplace book?
A commonplace book is a collection of passages, quotes, and words gathered over time, sorted under specific themes, subjects, or topics, and compiled into one book.
"We should follow, it is said, the example of the bees, who flit about and cull the flowers that are suitable for producing honey, and then arrange and assort in their cells all that they have brought in... We also, I say, ought to copy these bees, and sift whatever we have gathered from a varied course of reading, for such things are better preserved if they are kept separate."
— Seneca, Epistulae Morales, Letter 84
The commonplace book has been the intellectual backbone of deep thinkers for centuries. Thomas Jefferson kept two of them, a legal commonplace book compiled while he studied law in the 1760s, and a separate literary one he began as a teenager and kept for over a decade. Between the two, he collected passages from what he read, arguments he wanted to return to, and quotations that mattered to him. Both are now held at the Library of Congress, publicly accessible.
John Milton, poet and polemicist, kept a commonplace book during the English Civil War that held his reading notes, quotations, and political views. The original manuscript is held at the British Library, though a published transcription has been freely available since 1877.
Charles Darwin returned from his Beagle voyage in 1836 carrying years of observation, and the following year began a notebook devoted entirely to the question of how species actually change, the beginning of what became his theory of transmutation. His grandfather, Erasmus Darwin, kept a commonplace book of his own decades earlier, divided into three categories: medical practice, natural history, and engineering designs and inventions (Erasmus Darwin House).
How to start a commonplace book
1. Choose a few topics or themes that matter to you.
2. Give each one its own page or section.
3. Every time you read or encounter something that interests you, write it down under its matching theme.
That's it. It's that easy.
Citations.
Fulton, T. (2010). Historical milton: Print, manuscript, and political culture in Revolutionary England. Project MUSE. https://muse.jhu.edu/book/751/
Lunar Lecture – Erasmus Darwin’s ‘Commonplace Book’ and the Enlightenment Organisation of Knowledge. Erasmus Darwin House. (2024). https://www.erasmusdarwin.org/event/25th-anniversary-lunar-lecture-erasmus-darwins-commonplace-book-and-the-enlightenment-organisation-of-knowledge/
Ahern, J. (2026, September 10). How to make a commonplace book . CiRCE Institute. https://circeinstitute.org/blog/how-to-make-a-commonplace-book/