A non-omnipotent agent can actualize (e)—bringing it about that a snowflake falls when no omnipotent agent ever exists—but an omnipotent agent cannot actualize (e), since an omnipotent agent cannot bring it about that no omnipotent agent ever exists.

Note that (a) is a past state of affairs. Presumably, it is not possible for an efficient cause to occur later than its effect. However, an agent’s bringing about a state of affairs is a kind of efficient causation. Therefore, it is not possible for an agent to bring about anything that is in the past. In other words, it is impossible for any agent to have power over what is past. Hence, no agent, not even an omnipotent one, can bring it about that (a) obtains. Likewise, despite the fact that (b) can be brought about prior to \(t\), the impossibility of an agent’s having power over what is pas...