Why does limits of knowledge fail?

The most common reason limits of knowledge fails: Treating validation as proof of universality. The failure pattern is: you test a schema, it passes, and you unconsciously upgrade it from "validated within tested conditions" to "true in general." This is the ecological validity error applied to personal epistemology. Every validation has a scope — the conditions under which you tested. Extending a schema beyond that scope without additional testing is not confidence; it is extrapolation disguised as knowledge. The more successful your validations have been, the more dangerous this failure mode becomes, because repeated success creates the illusion that boundaries do not exist.

The fix: Select a schema you consider well-validated — something you have tested and believe to be true. Write it down as a single declarative statement. Then systematically probe its boundary conditions by answering six questions: (1) In what specific contexts have I actually tested this? (2) What contexts have I never tested it in? (3) At what scale have I observed it working? What happens at 10x or 0.1x that scale? (4) What population or situation type was present during my validation? (5) What would have to be true about a new situation for this schema to fail? (6) If I stated this schema to someone in a very different field or life situation, what objections would they raise? Write your answers. The gap between questions 1 and 2 is the gap between your validated domain and your assumed domain. That gap is where the limits live.

The underlying principle is straightforward: Even a well-tested schema may fail in new contexts or at different scales. Validation tells you where a schema works, not that it works everywhere. The boundaries of your tested conditions are the boundaries of your warranted confidence.