Failure is instructive. The person who really thinks learns quite as much from his failures as from his success.

The remark distills a central Deweyan theme: learning is an active, reflective process in which experience becomes knowledge only when it is examined. “Failure” is not merely a negative outcome but a diagnostic event that reveals mistaken assumptions, inadequate methods, or incomplete understanding. For Dewey, the decisive factor is “really” thinking—i.e., inquiry that tests ideas against consequences and revises them. In that frame, success can confirm habits without deepening insight, while failure can provoke analysis and growth. The quote also implies an educational ethic: classrooms and institutions should treat mistakes as data for inquiry rather than as occasions for shame or exclusion.