This article is first published in this series.
Keywords: topos, bicategory, 2-limits, classifying topos, geometric theory, factorization systems, spectrum
2010 MSC: 03G30, 18B25, 18C10, 18D05, 18D25, 16F10, 18F99
Reprints in Theory and Applications of Categories,
No. 25 (2016) pp. 1-16