We come to know what is real, then, in one of three ways. We can detect it directly, using our five senses; or indirectly, using our senses aided by special instruments such as telescopes and microscopes; or even more indirectly, by creating models of what might be real and then testing those models to see whether they successfully predict things that we can see (or hear, etc.), with or without the aid of instruments. Ultimately, it always comes back to our senses, one way or another.
