It's easy to claim there is an opposite for everything. Just assert its negation, e.g.., no telephone, no television.
I don't merely think by asserting a negative makes something it's opposite, Up is not the negation of down. Nor East the negation of West, if I traveled east on earth sooner or later I would wind up at my original starting place.
To say that the sun doesn't rise in the east is not the negation of saying the sun rises in the east, because in truth the sun doesn't rise at all.
what about idioms? When I say something is bad " man that's person bad " I'm giving the word a positive spin.
What if a person has a deterministic view of exist? I guess i'ts opposite couldn't exist meaning a person would believe there isn't such thing as free will.
After all, your question is phrased "Is there an opposite to everything we know?
What would be the opposite of "A cannot be true and false at the same time?