---
tag: 3YBZG77528
kind: concept
name: Modal collapse
sources:
  - wikipedia: en:70649628@r1371868244
    locator: Modal collapse
    note: adopted
    mention: wikipedia://en/70649628
    sections: [Summary]
same_as:
  wikidata: Q111745250
  wikipedia: Modal collapse
inventory: [ENS8E13FPN]
---

## Summary

In modal logic, **modal collapse** is the condition in which every true statement is necessarily true, and vice versa; that is to say, there are no contingent truths, or to put it another way, that "everything exists necessarily" (and likewise if something does not exist, it cannot exist). In the notation of modal logic, this can be written as $\phi \leftrightarrow \Box \phi$.