 The solutions in the second group, temporalized solutions, recognize the world’s ontological inventory has changed at \(t'\). For instance, Chrysippus, according to Philo of Alexandria, claimed that “it is necessary that Dion remains while Theon has perished” (Long and Sedley 1987, p. 172), so Oscar exists throughout the whole period, but Theon dies at \(t'\). Accepting some kind of mereological essentialism (Chisholm 1973), one may hold an opposite view: since all parts are essential to Oscar, the amputation event killed Oscar while Oscar− enjoyed existence throughout the whole period in question. Then you may maintain that the event at \(t'\) either (i) brought Oscar− into existence or (ii) did not disrupt Oscar−’s prior existence, so Oscar− existed at all times from \(t\) to \(t'\). Finally, a proponent of  contingent identity may claim that Oscar is at t different from Oscar−, but at \(t'\) they become identical. 