Static text forces a reader to either blindly trust or blindly doubt an author's claim, because the argument is fixed and there is no way to test it. Bret Victor's fix is the "reactive document" — an explanation where the reader can change the author's stated assumption (a tax rate, a compliance percentage) and watch the conclusion recompute live, the way a spreadsheet updates when you edit a cell. This reframes what "active reading" needs: not better reader discipline, but a different document format. A reader who wants to check "what if the assumption were 20% higher" normally has to redo the author's math from scratch, off to the side, disconnected from the text — so almost nobody does it, and unverifiable claims pass unchallenged by default. A reactive document puts the parameter in the reader's hands directly, turning "is this argument right?" from a research project into a five-second experiment. **Cross-Domain Connections**: The same move shows up any time a system converts "trust the stated conclusion" into "manipulate the input and watch the output" — an interactive amortization calculator versus a loan brochure, a spreadsheet versus a printed budget table, a policy explainer with adjustable sliders versus an op-ed's fixed numbers. [[PKM/Active Reading]] approaches the same problem from the reader's side (habits, note-taking, intention) rather than the document's side (format, interactivity). ## Source - [[20260805 Explorable Explanations]] — Bret Victor, March 10, 2011 — https://worrydream.com/ExplorableExplanations/