By the Necessity of Distinctness (ND), if two objects are distinct at one time, they are distinct at all times at which they exist

Oscar and Oscar− both survive Oscar’s loss of a tail. At both \(t\) and \(t'\) Oscar and Oscar− are the same dog, but at \(t\), Oscar and Oscar− are distinct logical objects. This implies (by ND) that Oscar and Oscar− are distinct logical objects even at \(t'\) Hence, we must allow that distinct logical objects may occupy the same space at the same time. This is not a problem, however. For although Oscar and Oscar− are distinct logical objects at \(t'\), they are physically coincident.