What is a commonplace book?
A commonplace book is a notebook where you copy down what is worth keeping from what you read: a passage, a quote, a fact, an argument, and a line about why it caught your attention. Over years it becomes a record of how you think, built from the best of everything you have read.
The idea is old. Renaissance students were taught to keep one, sorting excerpts under headings such as virtue, friendship or fortune so they could find and reuse them later. John Locke published a method for indexing his. Thomas Jefferson, Virginia Woolf and Octavia Butler kept them. The name comes from the Latin locus communis, a "common place": a topic you return to again and again.
Why the habit works
Reading is easy to forget. A week after finishing a good article, most of us remember the feeling and a sentence or two. A commonplace book changes that in three ways:
- Copying is a second reading. Choosing what to keep, and writing a line about why, makes you decide what the text actually said.
- Ideas meet each other. A note filed next to one from a different book, written years apart, is where new connections come from.
- It compounds. Every entry makes the collection more useful, because there is more for the next idea to connect to.
What goes in one
There are no rules, but most commonplace books collect some mix of:
- passages and quotes, with the source
- facts and figures you expect to need again
- arguments you agree or disagree with, and why
- questions you are still thinking about
- your own short reflections on any of the above
The part people skip, and the part that matters most, is your note. A quote without a reason is a bookmark. A quote with a reason is a thought you can come back to.
Commonplace book vs. journal vs. second brain
A journal records your days. A commonplace book records your reading. The two overlap, but a commonplace book is organised around ideas rather than dates.
A second brain or personal knowledge management system is the modern descendant of the commonplace book. The goal is the same: keep what matters, connect it, and use it. The difference is mostly in tools and in how much organising they ask of you.
Keeping a digital commonplace book
Paper still works, and some people prefer it. A digital commonplace book adds things paper cannot do:
- Capture from where you read. Save the article, paper, video or post itself, not only the line you copied, so you can return to the full context.
- Search everything. Find a passage by what it was about, even when you have forgotten the exact words.
- Keep the source attached. Every excerpt links back to where it came from.
- Let connections surface. Related entries can be found for you, instead of depending on the heading you chose years ago.
The risk with digital tools is collecting without thinking: saving hundreds of links you never read again. The old rule still applies. Keep less, write why, and revisit what you kept.
How to start
Start small. The next time something you read makes you stop, save it and write one sentence about why. Do that for a month, then read back through what you kept. Most people find the collection already says something about what they care about, and that is the point of a commonplace book.
We are building commonplot as a digital commonplace book: it saves what you read from the web, RSS, papers and video, keeps the source with every note, and lets you search and ask questions across everything you have kept.