The Eilu vaEilu Paradox
The notion of eilu va’eilu is taken by many to be quite literal — that two conflicting halachic opinions can both be equally correct, both equally truly representing the Will of G-d. This is a product of halakhah being a mapping from Hashem’s infinite Thought to human reality and/or His leaving us a process that has room for our creativity because that creativity is itself part of the redemptive process, etc…
Here’s the paradox… Say camp A holds that some limit X is involate, that people who deny X believe in heresy (albeit may not have the laws of a heretic). Camp B denies X, but has no similar red line that camp A crossed.
B is in the position of believing eilu va’eilu includes the truth of A’s approach to Torah — including the belief that B’s own approach isn’t true (isn’t within eilu va’eilu)? Paradox!
This comic presented a nice mashal, if you have some knowledge, even on the popularization level, of some of the odder hypotheses in physics: