# Constructivism

**Type:** Concept  
**Domain:** foundations-logic  
**Codex URL:** /mathematics/foundations-logic/constructivism/  
**Entry status:** Live — v1.0 (2026-07-09)

## Summary
Mathematical existence requires explicit construction. Rejects law of excluded middle. Brouwer intuitionism c.1907-1920s; Bishop 1967 constructive analysis; intuitionistic logic; Kleene realizability 1945; topos theory (Lawvere-Tierney 1960s-70s).

## Sources
- [Tier 1] Bishop, E. (1967). Foundations of Constructive Analysis. McGraw-Hill.
- [Tier 1] Troelstra, A.S. and van Dalen, D. (1988). Constructivism in Mathematics. 2 vols.
- [Tier 2] Dummett, M. (2000). Elements of Intuitionism. 2nd ed.
- [Tier 3] Bridges, D. and Richman, F. (1987). Varieties of Constructive Mathematics.

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*Mathematics Codex entry v1.0 — added 2026-07-09 — thecodex.expert/mathematics/*