Everything is proven by effect

Everything is "proven" by effect.  We know electrons exist because we measured their effects originally on oil droplets, then later in many other ways.  We never directly observe anything.  We are imagining all of it.  A theory is valid, essentially if it is proven useful... i.e. can predict something new, or allow us to design something new.   It's not that we are getting to truth, but rather removing our faulty assumptions, such as that only 3 dimensions exist (which is an assumption).