Again, it depends.
If the verse treats it as if you are literally summoning the concept of fire, then yes, you would need some sort of conceptual resistance to negate it, as it is not normal fire, but is the concept itself or at least spawned directly from it.
If instead, for example, the fireball is created through a Magic System that works through manipulating concepts (I.E. Aethyr Manipulation from Warhammer Fantasy), and instead of bringing the concept itself into reality, you are instead using that concept manipulation to create normal fire, it wouldn't require conceptual manipulation to resist, as in the end, you didn't summon the concept, you simply used something based in manipulating concepts to create something normal.
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