You never know exactly to what exact extent your map matches the territory. But you can have a pretty good idea. Like, we know (to the extent that we can "know" anything) that models predicting the Sun will rise tomorrow match reality better than those which don't. We know that models which predict that turning on a switch will cause the lightbulb to emit light are more accurate that those who say that it's magic or mysterious.
To quote Feynman:
> We’ve learned from experience that the truth will out. Other experimenters will repeat your experiment and find out whether you were wrong or right. Nature’s phenomena will agree or they’ll disagree with your theory. And, although you may gain some temporary fame and excitement, you will not gain a good reputation as a scientist if you haven’t tried to be very careful in this kind of work. And it’s this type of integrity, this kind of care not to fool yourself, that is missing to a large extent in much of the research in Cargo Cult Science.