SUMMARY

Chapter 4: Word and Line (200 Years: A Quarter Phase, ca. 850–1050) is focused on optics, a subject with major breakthroughs associated with Islamic lands. Here, the corresponding message is that besides roots through ancient Greek sources, routes through transmissions to Europe, and rules through Arab and Persian patrons, another component critical to both developments and non- developments is ‘books’. In this chapter, books are highlighted through an Arabic optical work with more outstanding impacts in Europe than its own native lands. Developments, non-developments, and partial developments are all from the two centuries following the initial scientific translations and transmissions, here termed a ‘Quarter Phase.’