If you're asking if there exists something that's 100% X at the same time as being 100% not-X, I'm not sure there's much to debate about it, as there clearly isn't (at least not in this world, where things can't seem to be themselves and not themselves at the same time).
"You are misusing the language, or rather I am in this case, to ask a paradoxical question. Where are all the cat dogs? This is a never ending game because we don't agree on the language. This is exactly the realm of metaphysics."
It's the realm of semantics (ie. definitions), but I'm not convinced that every metaphysical question could be reduced to a semantic one.
If you take the question of whether one has some sort of existence (like, say, as a "soul") before birth, I think that question would still exist even after we'd agreed on the constituent definitions. Also, I don't see anything paradoxical in that question. Even were it paradoxical, its paradoxical quality would in no way disqualify it for me. Perhaps I'd be even more interested in examining it, as examining paradoxes has been a very fruitful approach throughout human history.
"To me greatness could be quantified by how much progress has been made in answering the question. After a thousand years and possibly millions of lives wasted trying to answer "is there existence before this life?" we are not one single iota closer to an answer."
There have been answers, they just haven't satisfied everyone. The same could be said of pretty much every other great question, no matter whether the answers come from science, religion, philosophy, intuition, or elsewhere.