>>715886698>how is domain selection an ability?You mean the justification?
Think that the domains are representations of the different aspects of the god, so a god of healing and righteous war might have healing, good, renewal, strength, protection, and war domains.
A Cleric that's more about healing and being a good boy might choose two of healing, good, renewal and protection, while a Cleric that's more of a strike evil down where it stands might choose two of good, protection, strength, and war.
That kind of thing.
From a roleplaying perspective, that allows deities to have different groups of worshipers, either ranks within the same religious structure, or even separate bodies of worship that might even be at odds with one another, etc.
The real question is why domains don't play an even larger role in the Cleric's identity, mechanically speaking.
I think AD&D/D&D 2e worked like that with specialty priests and such.
Clerics in 3.pf are awesome, but they did get too broad what's with having full access to a whole ass spell list that's wholly divorced from their deity.