When determining a theories validity or comparing it to another let's say creationism and evolution it's put through the criteria of adequacy. And evolution come out on top on every field. Does that mean that it's absolutely correct? On some levels it could be (ie, natural selection is observable and changes within the species occurs all the time) but for the most part its just a superior theory than creation.
The criteria of adequacy are testability, scope, fruitfulness, conservatism, simplicity, I found a good example of evolution and creation being judged by both.
TestabilityA hypothesis is scientific only if it is testable, that is, only if it predicts something more than what is predicted by the background theory alone.
Evolution: Testable claims, about the fossil record of change in earlier species
Creation: Testable claims, About the fossil record
ScopeOther things being equal, the best hypothesis is the one that has the greatest scope, that is, that explains and predicts successfully the most diverse phenomena.
Evolution: Explains diverse phenomena, The fossil record of change in earlier species and the chemical and anatomical similarities of related life forms.
Creation: None. Creationism’s explanations are either failed explanations or pseudo-explanations.
FruitfulnessOther things being equal, the best hypothesis is the one that is the most fruitful, that is, makes the most successful novel predictions.
Evolution: Has predicted novel facts, Organisms should adapt to changing environments. Mechanisms for modifying features and passing them from generation to generation – genes and mutation.
Creation: Has makes mostly non-conservative novel claims, about buoyancy. Most adopt evolutions mechanisms to explain different traits in kinds of animals
ConservatismOther things being equal, the best hypothesis is the one that is the most conservative, that is, the one that fits best with established beliefs.
Evolution: Fits well with current established beliefs, such as the Earth’s history is much longer than several thousands years.
Creationism: Conflicts with well-established beliefs, Age of the universe, Buoyancy of earlier species, Types of fossils, Noah’s Ark and the great flood
SimplicityOther things being equal, the best hypothesis is the simplest one.
Evolution: Without postulating a supernatural being with supernatural powers, but natural mechanisms involved.
Creation: Postulating a supernatural being with supernatural powers, but less natural mechanisms involved.
So you can easily see that evolution is a superior theory.
But to me it's about faith. But I really don't want to get into a huge debate whether I'm right or wrong about this aspect of my life. So please no attacks. I accept my position is less than favorable without the assumption of a all-powerful God but I respect atheist and agnostics.
Sometimes I wonder if faith is what separates me from almost being agnostic myself, since I don't belief either can be proven beyond a doubt and I believe that God wanted it that way.