, Volume 187, Issue 2, pp 441-469

First online:

Open Access This content is freely available online to anyone, anywhere at any time.

Indeterminism is a modal notion: branching spacetimes and Earman’s pruning

  • Tomasz PlacekAffiliated withJagiellonian University Email author 
  • , Nuel BelnapAffiliated withDepartment of Philosophy, University of Pittsburgh


The paper defends an Aristotelian notion of indeterminism, as rigorously formulated in the framework of branching space-times (BST) of Belnap (1992), against criticism by Earman’s (2008) based on a model-theoretic characterization of indeterminism. It delineates BST branching against the background provided by Earman’s (2008) distinction between individual versus ensemble branching. Partly in order to motivate our responses to Earman, it describes a construction of physically motivated BST models, in which histories are isomorphic to Minkowski spacetime. Finally it responds to Earman’s criticisms leveled against BST by addressing a topological issue, the question of an actual future, the past/future asymmetry, and some semantical questions.


Indeterminism/determinism Spacetimes Branching space-times Tenses