What is model usefulness?

Model usefulness is a concept in personal epistemology: No schema perfectly represents reality but some are more useful than others for a given purpose.

Example: Newtonian mechanics is technically wrong — it ignores relativistic effects that compound at high velocities and in strong gravitational fields. But NASA still uses it as the primary framework for most orbital calculations. For the vast majority of spaceflight, Newtonian math is less than 0.0001% off from reality. It's wrong. It's also the most useful schema engineers have for getting things into orbit. Usefulness, not correctness, is the standard.

This concept is part of Phase 11 (Schema Foundations) in the How to Think curriculum, which builds the epistemic infrastructure for schema foundations.