 But the biggest problem concerned what became known as “late pre-emption”. In the rock throwing example above, we assumed that Billy decided not to throw when he saw Suzy throwing. But we can imagine a variant of the case where Billy waits to see whether Suzy’s rock hits, and only then decides not to throw. In such a case, it is the window’s shattering, not anything prior to this, that causes Billy not to throw. That means that there is no event between Suzy’s throw and the window’s shattering on which the shattering is counterfactually dependent.