Quote Originally Posted by bid View Post
If you are wizard 1 / cleric 16, your MC combination gives you the spell slot of a level 17 caster which includes a 9th slot.
Wish is a 9th spell.
A wizard's spellcasting feature allows you to add spells to your spellbook, "of a level for which you have spell slots"
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If you allow character level on warlock invocation, you necessarily allow (gate, true resurrection, true polymorph, wish) on character level. Which includes a bard 1 / cleric 1 / druid 13 / sorcerer 1 / wizard 1 character or any other combo with a 9th slot.
As far as I'm aware, no one has mentioned anything like this in the thread. It's spelled out pretty clearly that a wizard 1 / cleric 16 can't learn or cast Wish. You're the first person to suggest otherwise, so the only argument you've debunked is your own. It's true that there is ambiguity about this in the Spellcasting feature description, but this ambiguity is specifically addressed and clarified in the section on Multiclassing. No one except you is talking about this, you're the first person to bring it up.

I think what's being argued right now is if "your level" means your level in that class, or your character level. In the case of warlock invocations, it may not have been clear initially but it's been errata'd that they do, in fact, mean your warlock level.