Full Idea
The singling out of a substance at a time reaches backwards and forwards to time before and after that time.
Gist of Idea
Singling out extends back and forward in time
Source
David Wiggins (Sameness and Substance [1980], Pre 2)
Book Reference
Wiggins,David: 'Sameness and Substance' [Blackwell 1980], p.6
A Reaction
Presumably this is an inferred history and persistence conditions. Sounds fine in a stable world. We assume (a priori?) that any object will have a space-time line for its duration.