Oxford Languages says that a commonplace book is “a book into which notable extracts from other works are copied for personal use.”
Commonplace books are not to be confused with journaling, as journaling more so involves the documentation of one’s personal life and inner dialogue: we can see this being done in the social media of today as people spill their innermost confessions online for no one and everyone to see.
Commonplace books are meant to compound thoughts and information from sources other than the self. Of course, if it was an interesting event or an epiphany experienced by the self, it should be included as a personal anecdote to preserve for later reflection.
Storage of commonplace books can take on different forms according to one’s preferences. It is recommended that one try out various versions just to see how their notetaking is influenced, or how their reflection readings form unlikely connections between passages. Below are a few examples:
Notebook: Less flexibility, but more convenient for travel and storage. You can write quotes in line by line and use symbols or colored markers for different topics for quick reference in the future.
Index Cards: High flexibility and opportunity for organization, but storage can be troublesome. Quotes can be written card by card and divided into different subjects easily.
Digital Apps: Convenient travel and a variety of formats depending on which app you use. Some unorthodox uses of different apps can result in some interesting compounding, like using a character planner as a commonplace book where each character represents a subject, or each quote (regardless of subject) correlates to a character’s characteristics in some intuitive way.
You can really get creative with it.
Commonplace books are typically used to store information that the owner appreciates or finds useful. Like a post-it on a full-blown research paper.
The sources of information do not have to be official if you intend on researching the topic yourself later on with the quote as an addendum. In fact, the “information” does not have to be entirely scientific, but instead a purely interesting or amusing quote from a friend.