 Finally, it’s important to remember that this dilemma and the need for a Past Hypothesis are dependent upon a particular physical set-up. Can we explain the thermodynamic arrow without invoking a Past Hypothesis? Inspired by the idea of eternal spontaneous inflation, Carroll and Chen (2004, Other Internet Resources) describe a model in which new baby universes (or “pocket universes”) are repeatedly born from existing universes. Each birth increases the overall entropy of the multiverse although within each baby universe we have our familiar thermodynamic asymmetry. The crucial assumption in this model – one also found in the gravitational theory of Barbour, Koslowski, and Mercati (2014) – is that entropy is unbound. It can be arbitrarily high. With this assumption and in these models, one can do without a past Hypothesis. For discussion, see Goldstein, Tumulka, &amp; Zanghi 2016 and Lazarovici and Reichert 2020.