Okay, so here's a question. Let's say that an alternative class feature for Cleric (or any other class with Orisons or Cantrips) states that you lose the Orisons ability.
--
Quoting from the SRD:
Orisons Clerics can prepare a number of orisons, or 0-level spells, each day, as noted on Table: Cleric under “Spells per day.” These spells are treated like any other spell, but they are not expended when cast and may be used again.
--
So here's the question. If you give up Orisons, do you lose the 0 level spell slots themselves, or do you only lose the ability to cast them without expending them?
It may seem obvious, but the Orisons ability is separate from the class spell chart which lists a 1st level cleric getting three 0-level spell slots.
So, would the cleric keep 0-level spells, but once cast they're gone (like normal 1st level and higher spells), or do they lose 0-level spells entirely?
Since Orisons references the chart, that means that part would be lost as well.
For an example of something exactly the same, any wizard archetype that loses Cantrips gives you detect magic and read magic as first level spells.
Well, you are roving outside the purview of this rules forum, because under the rules of the game, there is no way to lose your orisons/cantrips. So if you somehow did, it would have to be through some homebrew situation, and that means you should really be over in the homebrew forum.
That said, if this is the ability you mean (cleric version):
Orisons: Clerics can prepare a number of orisons, or 0-level spells, each day, as noted on Table: Cleric under “Spells per Day.” These spells are cast like any other spell, but they are not expended when cast and may be used again.
Then if you lost it, you would lose the ability to prepare zero level spells and the ability to "not expend" them when cast. You would have slots into which you could not prepare spells, and when you used those slots, which you couldn't, you would expend them in so doing.
But really, we're into the weeds of a non-rules-based absurd hypothetical, here.
You lose all ability to cast 0 level spells. For reference, see the Mage Bullets ability of the Spellslinger Wizard.
Cool - thanks all!