I'm too much an instrumentalist to give you an unbiased answer. My view is that, as it pertains to any theory, the ability to make reasonably accurate predicti

I'm too much an instrumentalist to give you an unbiased answer. My view is that, as it pertains to any theory, the ability to make reasonably accurate predictions within a given region, and reasonably accurately describe the region where those predictions are correct is understanding. I don't believe our knowledge is complete, because the universe is effectively infinite, so there's room for effectively infinite combinations and permutations of phenomenon even within our understanding. But when we encounter something that contradicts our understanding, that doesn't mean we didn't understand anything we experienced before. It just means that our overall understanding was incomplete.