Ironically Plato takes this into account in his allegory. There are lots of levels to “knowledge” (which he equated with goodness); we could be in the same spot just with our heads turned, or right behind the wall, or outside the cave but looking at the reflections in the water. And in each stage everyone believes they’re right and that they know the truth (except maybe in the last one). Honestly I think with fedi we just managed to turn our heads.