Everything exists solely by comparison. Happiness cannot be felt without sadness and anger to compare it to. If the latter two did not exist, happiness would not be a phenominon, but instead the usual, and in this case only, state of being. This means it would become the new 'neutral' emotion, because it would be the natural state of being, with nothing better or worse off.
Using this reasoning, there could be no light versus dark. No good versus bad. Without a second state to compare either to, they are just a singular state. A known and proven fact that could never be changed or broken. There could be no life versus death. Nothing would exist, yet at the same time, everything would exist, because 'nothing' is also a state, as is 'everything'.
Everything and nothing can be both proven and disproven all at once because our knowledge of what is real is based off of what we have observed, and if we have only observed one side of a dispute, then there is still the chance it can be disproven. We accept gravity as a solid fact, yet only because the knowledge and experience we currently have supports the idea. Someday, we may be disproven because new information or events have occured.