Second Brain

A second brain is an external, searchable system that stores what you'd otherwise have to remember — notes, decisions, documents, ideas, commitments — on the theory that your head is for having ideas, not for holding them. The term comes from the personal knowledge management world, where the second brain was a well-organised notes app.

The AI generation of the idea goes further: instead of you searching your notes, an assistant grounded in a personal knowledge base answers from them — and captures new material as fast as you can send a message. Combined with follow-up tracking (remembering your open loops) and a daily brief (resurfacing what matters today), the second brain stops being an archive you maintain and becomes a colleague who never forgets.