What is information hierarchy?

Example: Your personal knowledge system has 300 notes. Without intermediate levels, you face 300 items in one list — impossible to scan. With three top-level domains and no middle, you pick a domain and still face 100 items. Add an intermediate layer — 8 to 12 categories per domain — and every navigation step reduces your options to a manageable set. You never see 300 items. You never see 100. You see 10, then 10, then the note you need.

This concept is part of Hierarchy and Nesting in the How to Think curriculum, which builds the epistemic infrastructure for hierarchy and nesting.