DRAFT
Observed
Objects without instance variables can't exist
Objects can have any number of instance variables, including zero
Even if an object has no fields, it still is an object and it still is allocated on the heap. It may be very small (because it has no fields), but it still exists and it still uses some memory (e.g., at least it has some meta information that determines what class the object has).
The identity of an object can be useful, even if the object contains no state otherwise.