<p>We normally think of the past as being fixed and unalterable. Many philosophers have held the same view about the future. Our actions may be able to <i>influence</i> the future by bringing about certain events, but we do not <i>change</i> the future since it will always have been the case that the relevant events were going to be brought about in that way. This is the standard view. The standard view has been challenged by a number of philosophers—most notably, Peter Geach. Geach’s view has seen renewed attention in recent years, but I will argue that the original impetus for the view is mistaken. Geach’s argument for the mutability of the future fails, and this failure has important things to teach us about the nature of prevention, the requirements for change, and the semantics of past-tense progressives.</p>