In a nutshell, theories are explanations using proven hypotheses to determine an event or phenomena. The evidence of the supporting hypotheses are so overwhelming that there is no other explanation that would logically work. Unfortunately theories are not able to be proven in many cases and therefore often leave some doubt. Take the “Theory of Evolution” the main supporting hypothesis is that creatures “evolve” and adapt to their environment. This has been proven over and over in the fossil record as well as during recorded history.
Species adapt to their environment to gain an advantage. But there are some things that defy adaptation. Say, a reptile changing to a mammal. This has never happened in human history nor is there any evidence in the fossil record, yet this has to be true for evolution to work. The evidence and proven hypothesis of micro evolution only loosely supports macro evolution. We can assume that this may have happened this way, but it’s no more a faith issue than believing in the Almighty God.