What an account is for
- It remembers what you know. Mark a concept known and every route you ask for afterwards skips it — and skips everything it implies. A route to Black–Scholes is 19 concepts from nothing and 2 if you already hold risk-neutral pricing.
- It keeps your notes. On a concept, or loose in a notebook for the thoughts that belong to no single one. Private to you.
- It lets you say we are wrong. Guides here are written and fact-checked by machine and published with no human reading them first. A reader who follows a citation and finds the page does not say it is the last line of defence.