Phil Pickering

Inspired by David Lewis’s work on possible worlds, there has been some discussion about whether the fission of worlds in the quantum many-worlds theory should be considered branching (where fission is like a branching path) or diverging (where the worlds are separate but qualitatively identical until some point of divergence). Several authors favour the latter on the basis that we can delineate worlds that are separate from each other prior to fission using a consistent histories approach. However, these worlds are not entirely independent of each other prior to fission, rendering neither of Lewis’s options fully compelling. I propose that the process is better conceptualised as splitting, analogous to the splitting of classical waves. When an entity splits, it separates into its component parts, each reduced somehow from the original, and so the original entity only partially persists as each of its successors. I propose that understanding many-worlds fission as one world splitting into its component parts aligns more closely with the physics and provides a more natural and intuitive understanding of the fission process.