13.2 When actualities at points in ordinary space and time
Unchanging Continuant (Substance)
is a separable propensity field. It endures unchanging between two
Changeable Continuant (Substance)
is a succession of `unchanging continuants' such that its adjacent and
successive stages satisfy that:
there is some event over which the two `unchanging continuants',
as propensity fields, are extensively continuous with each other. This
event would then be the product of the earlier continuant and the cause of
the later one.
these two continuants have the same `substantial form' even though
they do not extend over the same sets of places.