The Commonplace Book

A personal library of passages, indexed by topic.

A commonplace book is a notebook into which a reader copies the passages worth keeping: arguments, definitions, proverbs, numbers, lines that changed their mind. Each entry carries its source, and an index at the front makes every entry findable by topic. It differs from a diary, which records days, and from notes, which serve one book and are forgotten. The commonplace book serves the reader across every book, for years.

The practice is ancient and distinguished. Aristotle taught collecting arguments under topics. Marcus Aurelius's Meditations is a commonplace book that became a classic. Erasmus made the method standard in Renaissance schools. John Locke published his indexing system in 1685, and it worked well enough that printers sold blank books with Locke's index pre-printed. Thomas Jefferson kept two. Benjamin Franklin's virtue ledger, in the Autobiography on the Entrepreneurship track, is a commonplace book turned on its keeper. The modern zettelkasten is the same idea on cards.

Six rules, one habit.

1. One passage per entry. Copy the passage exactly, in your own handwriting. Copying slowly is the point; it is the difference between reading and keeping.
2. Every entry gets a source line. Author, title, and page or chapter. An unsourced quotation is a rumor.
3. Every entry gets a topic word. One or two words in the margin or above the passage: COURAGE, PRICES, QUEUES, TRUST. Choose the word you would search for later.
4. Add one line of your own. Below the passage, one sentence: why you kept it, what it connects to, or what you disagree with. This line is where thinking happens.
5. Index as you go. Reserve the first four pages of the notebook for the index. When you finish an entry, write its topic word and page number in the index. Locke's method: organize the index by first letter and first vowel, so CoURAGE files under C-o. A simple alphabetical list works too.
6. Reread monthly. Once a month, read the whole book front to back. Old entries meet new ones, and the connections between them are where original thought comes from. This is consilience practiced by hand: when passages from different journeys say the same thing, mark them with each other's page numbers, and when three journeys agree, record the principle on a cross-reference sheet. Section 03 shows one worked through.

Nine entries, three journeys, one principle.

These are the entries a reader might make across three journeys: J04 The Flow of Work, J02 The Invisible Hand, and J06 Minds & Machines. The journeys share no authors and no subject. Read down a column and each journey makes its own case; read across a row and the three fields turn out to be making the same one. Each column holds a claim, the mechanism behind it, and a test a reader can run in the library.

The page numbers are the reader's own notebook pages. The last line of each entry records its connections, which is how the cross-reference at the bottom was found.

Three sheets, each shown blank and filled in.

Print only the sheet you need. Each one is a single page, in A4 for the library program and US Letter. The filled copies use the worked example above, so a reader can see what goes in every box before writing in their own.

Where to get one, or how to make one.

The primary source, free

Locke's essay "A New Method of Making Common-Place-Books" (1685, English translation 1706) is public domain and short. It is in the canon on the Language & Rhetoric track. Print it and shelve it beside the notebooks: the method, taught by its author, sitting in the library it serves.