15 December 2025 – Stephan Leuenberger (Glasgow) – “In search of personal time”
Aula “Martinetti”, Via Festa del Perdono 7, h. 15:30
Abstract. The standard account of time travel takes it to be a discrepancy of personal time and external time. David Lewis’ “The paradoxes of time travel” (1976), the source of the standard account, defines distance in personal time in terms of the quantity of certain species-typical qualitative changes (growth, ageing, etc). This account is beset by difficulties, as pointed out by critics. In a book manuscript on time travel from 1971 recently published from Lewis’ Nachlass, Lewis offered a different account of personal time, in terms of causal relations between stages (immanent causation, effectively, as in Effingham (2020).) This account equips personal time with an order and a topology, but not a metric. In this talk, I shall develop this account to accommodate loops in personal time, and argue that it gives us a better definition of time travel than Lewis’ better-known later proposal.