In philosophy, e.g. in Spinoza, there is the Latin word "potentia" that is often translated as a power, or capacity, to act (potentia agendi) and to suffer actions.
I am wondering what is the right declination of "potentia" in a sentence like this: "George is violent in potentia." By this sentence I mean that "George is capable, by means of his power/potentials/capacities, to commit violence and to suffer violence."
So, what is the right form of "potentia" in the combination "in potentia"? Is it "in potentia" (ablative) or "in potentiae" (dative)? Or is the preposition "in" wrong and it is "qua potentia" or "per potentia" or something like that?
If we wouldn't use potentia but potestas, would we say "in potestas" or "potestate" (without "in")?
Note: I'm not aiming to translate the whole sentence, but I am actually using the Latin phrase "[in] potentia" in a German or English sentence. Still, it needs to be in the right declination.
Thanks a lot!