It's partly a question of definitions. There's an astrological phenomenon that occurs when large masses collapse, and we believe there is one of those at the ce

It's partly a question of definitions. There's an astrological phenomenon that occurs when large masses collapse, and we believe there is one of those at the center of the Milky Way. This exists in nature, we just haven't definitely figured out how they work yet. We currently call those "black holes". If a new theory suggests that these holes are not so black, but really rather "grey holes" or something, we might adopt a new word for those things, or we might change our definition of black hole to match the current theory.