Comment by throwway120385

A good example of this would be the scope of our sense of sight as it relates to the entire electromagnetic spectrum. We can't see things like UV or Gamma radiation, we can only infer their existence by their effect on things we can see. The reality is that those phenomena might not actually exist in any perceivable way. The only thing we know, strictly speaking, is that the effect happens, and we have a plausible mental model for why the effect happens that predicted other effects that we also observe. But we can't prove that the mental model is reality.

This is at the heart of the Allegory of The Cave: https://en.wikipedia.org/wiki/Allegory_of_the_cave. What we're discussing is a kind of "Natural Philosophy" or Physics, the study of that which is.