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