Localization and Its Universal Property

Prerequisites. Direct starred prerequisites: none. No later core chapter depends on this route.

Opening obstruction

A reflective subuniverse becomes a localization only after specifying which maps are inverted and proving the universal factorization property.

Development contract

Construct localization at a family of maps, prove its induction and universal property with closure hypotheses explicit, and derive the selected modality comparison without making localization a premise of the earlier core factorization chapter.