In philosophy it is common to introduce a high-level ontological distinction between continuants and occurrents. Continuants are entities which endure through time: for this reason, they are also called endurants. A continuant can undergo change and yet preserve its identity through those changes. Its parts are spatial parts, and it exists, as a whole, at each moment of its lifetime-notwithstanding the possibility that at different moments that whole might consist of different parts. Occurrents, on the other hand, are extended in time: they ?perdure? (hence, they are called perdurants). Unlike continuants, occurrents have temporal parts, e.g., the first half of the concert and the second half of the concert. Because an occurrent as a whole spans the time period from its beginning to its end, it cannot be said to change (although it may be a change), and it does not exist, as a whole, at any one moment during its temporal extent.