How the Locke index works

The short version

John Locke, the English philosopher, described a method for keeping a commonplace book (a notebook for ideas, quotes and things you read). It first appeared in print in French in 1686, and the English edition, A New Method of Making Common-Place-Books, was published in London in 1706.

Instead of dividing a notebook into sections in advance, you write notes as you go, and keep a small index at the front. Each topic is filed by two letters.

1. Name the topicGive each note one key word that says what it’s about, and use the same word each time you return to the topic.
2. Find its two-letter codeTake the first letter of the word and the first vowel after it (a, e, i, o or u). Treat y as i. If there is no vowel after the first letter, use the first letter twice.
3. Look it up in the indexIf the topic is already listed under that code, turn to its page and keep writing. If not, write the topic and your current page number in the index. When a topic outgrows its page, add the next page number beside it.

Examples

Topic	Code	Why
Leadership	Le	L, then the first vowel, e
Logistics	Lo	L, then o
Budget	Bu	B, then u
Ethics	Ei	E, and the first vowel after it is i
Art	Aa	No vowel after A, so A is used twice

Try it

Why it works

Because topics are filed by letter pairs and not by section, you never have to guess how much room a subject will need. Each note takes the next free page, the index remembers where everything went, and a See-also line links related pages. Twenty-six letters and five vowels give 130 possible codes, and the whole index still fits on just a few pages.

The Lockebook is a ready-made notebook built on this method: 186 numbered pages, a 6-page index and a worked example. It is not required. You can try the method in any notebook with numbered pages.