During the Renaissance, scientists, and thinkers often compiled journals filled with formulas, quotes, ideas, letters, poems, and more. They were organized by topic rather than chronologically. Usually, they were used as a personal database for indexing and remembering knowledge.
John Locke wrote a how-to titled Method for Common-place Books. Some of the main takeaways:
Organized by topics rather than chronologically
A method to index content to make it easily accessible.
An adaptable system that allowed entries to expand and new ones to be added.
Commonplace books should not only be used for recording useful knowledge but also for synthesizing it.
Famous examples:
Isaac Newton developed the foundations of calculus in his commonplace book (he called it his “waste book”.
Francis Bacon compiled phrases and proverbs in his commonplace book.
Thomas Jefferson
John Milton
As my favorite professor Dr Tim Duggan said (and I often repeated), “Writing leads to discovery.”