For example: it seems natural to describe the motion of a ball in terms of its altitude. The point is this: I can’t think of any example of putting together two negative things and getting a positive thing, that couldn’t equally well be thought of as putting together to negative things and getting another negative thing. For example: the force between two negative charges is repulsive. So if you want to define “apart” as positive then two negatives (charges) makes a positive (force). But if you define “together” as positive then two negatives make a negative.