Machine derived contents note: List of figures -- Preface -- List of abbreviations -- Introduction -- 1. The primacy of sight -- 2. The fallacies of sight -- 3. The harmony of the spheres -- 4. The harmony of the senses -- 5. The common sense -- 6. Spiritus -- 7. The light of the piazza -- 8. Optics and the commonsense -- 9. Confused knowledge -- 10. Cogitation -- 11. The mechanical arts -- 12. Prudence -- 13. The spark of God -- Conclusions -- Bibliography -- Index