 Abelard assumes that at a given instant of time, what is actual is necessary as no longer avoidable, but he argues that unrealized alternatives are possible at the same time in the sense that they could have happened at that time. Some of the alternatives of a singular being are real counterfactual alternatives. These are unrealizable because of some previous change in the conditions of the subject, and some are merely imaginable alternatives, such as Socrates’s being a bishop, which never had a real basis in things. While often employing traditional ideas about necessity and possibility, Abelard also developed ideas pertaining to simultaneous alternatives. (See Martin 2003; Knuuttila 2008: 537–538.)