"Fact - you know that person has walked across each capital / has walked in each capital
Assumption - that the person has walked around the world"
Ok, this is hilarious, but I'll continue for the fun of it. Where you have used assumption, what you actually mean is theory.
What you mean to say here is
"FACT: people walk, I saw this person walking in many places" and
"THEORY: they walked around the world".
There is also
"THEORY: They used some other form of transport in between when you saw them",
"THEORY: They are actually different people",
"THEORY: You have some kind of visual/mental distortion occurring where you think its the same person but it actually isnt"......and many more. Science is the process of getting all those theories in and then investigating in as many ways as possible what other information we can get in an attempt to DISPROVE the theories.
Science isnt about trying to prove things, its about trying to disprove things and not being able to do so. Thats why everything is a theory for ever, because some new thing could come to light to disprove gravity, or magnetism, or anything. People seem to think that because something is a scientific "theory", that means that everyone is very uncertain on whether they think its actually true or not, thats fundamentally incorrect.
Taking one theory and saying "this is the one truth forever" is the preserve of religion.
And as to the idea that God must have made the mountains because they are so awesome, just try and imagine it from the point of view of something that isnt Human - I'm sure a very deep-sea creature that can only live under massive pressure would find the existence of earth-atmosphere mountains utterly repulsive and horrifying, as would something that lives on the surface of Venus, or Saturn. Humans find them pretty and nice because they are the environment that suits us.