 Various problems can be raised for this account. The most obvious is that it does not, as stated, distinguish between substances and events. Some property-instances belong to events rather than substances. The performance of a symphony, for example, is an event, and it may possess the property, in one of its movements, of being allegro. It seems plausible that this particular case of something’s being allegro could not have been exemplified by another performance, but the performance might go on to be andante in another movement, so the event can continue to exist without that original property. The assimilation of events with substances in this way seems strained, however. It does not seem natural to say that the same event was first allegro, then andante, because it is more natural to attribute the different properties to different parts of the event, which are themselves events (in this case, movements). This brings out a major difference between substances and events, namely that the temporal parts of events are themselves events in their own right, but the temporal parts of objects—meaning by that expression the temporal phases of an object’s existence—are not themselves objects. Indeed, it is not natural to talk of the temporal parts of objects, though some philosophers (led by David Lewis (1986), but see also Sider (2001), Hawley (2001) and the entry on  temporal parts)  think that there are compelling philosophical reasons for doing so. The rationale implicit in our ordinary concept is that an object is wholly present at all the temporal points of its existence. I say ‘implicit rationale’, because it seems no more natural to speak of an object as being ‘wholly present at all temporal points of its existence’ than it is to say that it has objects as its temporal parts. Nevertheless, one does not think of a long-lived object as consisting of a series of short-lived objects stacked end to end, but one does think it natural to think of a drawn-out event as consisting of a series of shorter events. If it is not natural to think of objects as having objects as their temporal parts, this seems to commit one to thinking of objects as wholly present at all times of their existence, strange though this form of expression may also be.