Is there a difference in meaning between argumentum ad and argumentum a? Does the latter even have authoritative usage in Latin?*
Here are some samples that I've found, not always from authoritative works, which seem to follow an interesting pattern:
argumentum ad misericordiam: an appeal to mercy or pity, attempting to override the law or truth
argumentum ad hominem: an appeal specific to the person you're trying to persuade, i.e. telling each person a different story, hoping to get them all on your side; or, in contemporary usage, trying to get the faults of a person who advocates an idea to rub off onto the idea
argumentum ad populum: an appeal to the people at large, i.e. arguing that the idea is popular, not that it's true (or perhaps arguing that since it's popular, it's likely true)
argumentum ad baculum: an appeal to force ("the stick"), i.e. convincing by threat rather than by enlightening
argumentum ad verecundiam: an appeal to reverence; I once read verecundia explained as the kind of bashfulness that you feel in the presence of something great or socially important, so that appealing to this emotion works like this: "How could say such an awful thing about our church?"
argumentum a simili: an appeal to similarity: since this is similar to that, the rule for that applies to this
argumentum a contrario (or e contrario): an appeal to the contrary: since this is different from that, the rule for that doesn't apply
argumentum a coherentia: an appeal to internal consistency: a proposal to resolve a conflict between rules that keeps the system of rules coherent
argumentum a fortiori [ratione?]: an appeal to a comparable, stronger case where the result is known
The pattern appears to be as follows:
Ad introduces something about who is judging the matter: their emotions, their loyalties, their numbers, their power or lack of it—all matters that are outside the matter under consideration.
Ab introduces something within the topic: a kind of fact, a relevant factor, a relation between the present case and a known or settled case.
Is this right? Is there an authoritative source about this? Or can you point to common usages of argumentum or ad/ab in other contexts that might serve as a precedent for the pattern above?
*Not just classical Latin.