When I was in college I would frequently have to write proofs for theorums. A "proof" is the logical consequence using deductive logic. If inductive logic is used then it has to be shown for every instance of the statement. To disprove a general statement -all you need is one example to disprove the generalization.
What all this means is that "Proof" in the real (non mathematical) world is hard to find. Sometimes what seems to be true is actually just true in a limited circumstance.
People in general are very illogical. They like their truths in neat little statements. Sometimes the truth is more complicated than what is initially thought. Sometimes the truth changes over time and sometimes, our perception of truth changes.
I suppose all this pondering really relies on the supposition that there is something outside myself which is consistant and actually exists. Furthermore it is assumed that we can really know something about it.
In the end -outside of mathematical proof I don't really know the nature of the world and nobody does. David Hume said it best: