Theoretical bug

[Oralee]

When you discover that your code is not giving the right results, not because there is any bug in your program, but because there is a bug in the theory on which it is based.
[Theoretical] bugs are rare but more common than thought. When you find one, [your perception of] the world improves quantically.
A more day to day example, it is when you realize something you never saw before, not because it was not there, but because your [mental model] of the world didnt include it.