Discussion Forum—A Way with Words, a fun radio show and podcast about language

I don't know about opposite, but the (mathematical) inverse would be a "halfadox."

The word "sensatez" is a noun that can be translated as the "a characteristic of a person who has sense".
Some synonyms I found are prudence, reason, reflexion(ponder), logic, good judgment,sanity, wisdom, although I guess the person acting with "sensatez" would have more than one of the synonyms I just mentioned

If I had to use it I would say:

"la sensatez de su discurso es sorprendente!" (the "sensatez" of her/his discourse is surprising)
Si actuas con sensatez, seria lógico que todo te salgan bien" (if you act with "sensatez", it'd be logical that everything will end up all right)

I think that to really answer this question, one must first consider what the opposite of a paradox IS before one can find a word for it.

If one considers a paradox to be a seeming contradiction that represents a deeper truth, then what is it's opposite?

A seeming contradiction that is, as it seems on the surface, represents a true contradiction?
A seeming non-contradiction that represent a truth?
A seeming non-contradiction that represents a falsity?

I would suspect that there is actually NO opposite of a paradox.

Perhaps a tautology. A tautology is inherently true or synonymous yet adds nothing to our understanding of reality. It would seem to qualify as the opposite of both of your criterion for a paradox.

I hope this helps.

Best wishes,
Shaun