What is internal vs external cognitive agents?

Internal vs external cognitive agents is a concept in personal epistemology: Internal agents run in your mind while external agents are embedded in tools and systems.

Example: You have an internal agent that fires when a colleague says 'this should be quick' in a meeting — it triggers suspicion and prompts you to ask for a time estimate. You also have an external agent: a calendar reminder every Friday at 4pm that triggers a weekly review. Both are agents. One runs on neurons, the other runs on software. Both reliably produce action from a trigger without requiring you to remember or decide in the moment.

This concept is part of Phase 21 (Agent Fundamentals) in the How to Think curriculum, which builds the epistemic infrastructure for agent fundamentals.