How can you actually know anything?
This question has interested me since I was a child. If you think about it, all sorts of things could be true...I mean it's logically possible that there could be invisible, inaudible, intangible fairies at the bottom of my garden (an example of the "underdetermination of theory by fact"). Imagine arguing with someone who believed that they did - is there anything you could say to change their mind? (you and the fairy-fancier would be working with "incommensurable paradigms").
However, If you want to know how the physical world works, your best bet is to go at it using what is known as the 'scientific method'. The demonstration of this is not difficult: a few centuries after Galileo, here we all are, surrounded by powerful science-based technology (which most of us don't remotely understand).
But if you ask why the scientific method gives such good results, or if you ask for more precise details about it, the answer is not clear or definite or agreed. This question is not itself a scientific one: it is a philosophical one. Even if you say "but this doesn't really matter does it?" that is itself a philosophical assertion.