I have read multiple questions on this site on Latin plurals, and I’ve learned that you can use both English plurals and Latin plurals with words which originate from Latin (e.g. referendum - referenda/referendums). I however have a somewhat different question:
An example - When reading a text full of fallacies, like for example the argument from ignorance - argumentum ad ignorantiam, you often need to use plural forms to show that a text is ridden with them. How do you pluralize these types of Latin “word groups”?
If I extrapolate the rules which I have read from the other questions on the site, it would be (taking the argument from ignorance for example) both argumentum ad ignorantiams (or something similar) and argumenta ad ignorantias (argumentum is neutral, so the plural is argumenta, and ignorantiam is feminine accusative because of the preposition ad, so it becomes feminine accusative plural which is -as). However, the first form just seems totally wrong. Is this still legitimate? Or would the only option in these cases be correct Latin plurals?
P.S. I know you all probably think “why don’t you just say arguments from ignorance”, but I feel this could come in useful in other cases, for example in legal terminology.