This article deals with the debate on whether it is possible for God to perish the existing world. This debate appears in the works of Islamic thought in the context of the post-eternity of the universe. The Felāsifa argue that the universe is necessarily past-eternal and post-eternal. In opposition to this view, it is argued that the universe is not eternal but created and that the post-eternity of the universe is not necessary but possible. In defence of the eternity of the universe, the Felāsifa rely on the claim that the universe's annihilation is impossible. Accordingly, the annihilation of the universe cannot be the act of an agent. For for an agent to be an agent, its action must be related to an existent. However, since non-existence is not an existent thing, the philosophers regard the non-existence of the universe as impossible and assert that the post-eternal existence of the universe is necessary. The strongest objection to this is that the non-existence of the universe can be grasped by reason and that there is no impossibility in God's realisation of something that can be grasped by reason. In the final analysis, this argument attributed to the philosophers is not strong enough to prove the impossibility of the annihilation of the universe, and these claims are open to debate.