The antonyms for the phrase "taken as known" could include "unknown," "mysterious," "ambiguous," "unclear," "inconclusive," or "controversial." These words represent concepts that are in opposition to the notion of something being taken as known, indicating that there is still much to be discovered, understood, or debated about a particular topic. For instance, if a scientific study yields inconclusive results, it means that the hypothesis cannot be taken as known because there is still too much uncertainty remaining. Similarly, in the field of politics, a controversial issue may not be taken as known because there are still many differing opinions and interpretations of the facts.