The situations of a physical object are conditioned by uniqueness and continuity.

The uniqueness is an ideal limit to which we approximate as we proceed in thought along an abstractive set of durations, considering smaller and smaller durations in the approach to the ideal limit of the moment of time.

In other words, when the duration is small enough, the situation of the physical object within that duration is practically unique.
The identification of the same physical object as being situated in distinct events in distinct durations is effected by the condition of continuity.

This condition of continuity is the condition that a continuity of passage of events, each event being a situation of the object in its corresponding duration, can be found from the earlier to the later of the two given events.

So far as the two events are practically adjacent in one specious present, this continuity of passage may be directly perceived.