 One metaphysical problem concerns how change is possible (this has become known as the ‘problem of temporary intrinsics’ or sometimes the ‘problem of change’). The banana in the fruitbowl was unripe a few days ago, and today it is overripe. Surely nothing can be both unripe and overripe?  Of course, it’s the fact that the banana is unripe and overripe at different times which saves it from metaphysical peril: we all know that. But it would be nice to understand why this fact is crucial: what is it about the passage of time which makes it possible for one and the same object to have apparently incompatible properties?