The idea-notebook originates from the English Enlightenment-era tradition to keep a so-called commonplace book. Intellectuals in the 17th and 18th century would assemble their own personalized encyclopedia of quotations by filling their books with interesting passages from their readings. They created their own memory-bank of knowledge, and even thought up indexing systems for these. Darwin’s Grandfather Erasmus Darwin – a physician, philosopher and inventor – kept one of the most famous commonplace books from that time and certainly did his part in inspiring his grandson.