If the expression "out of sight, out of mind" is true, then we would have to see everything in order to think about it. Amirite?

And what does "out of sight, out of mind" do to the expression "seeing is believing." Sort of creates a real conundrum now doesn't it?
If the "out of sight, out of mind" phrase is true, then it also seems that our thoughts would be restricted and limited to ONLY the things we can see. Personally, I have thoughts about things I never see or never have seen.
I welcome you take on this concept.