A theory is not a matter of faith. Do you have faith in gravity or the presence of tiny bacteria that make you sick? Those are both "theories".
Read:
http://www.religioustolerance.org/ev_stat.htm
Not only that, Evolution is not even a Theory. It's a Fact. We can SEE that organisms change over time in the fossil record. Nobody is debating the absolute FACT that organisms can change over time, most likely due to changes in DNA.
The THEORY of Evolution deals with the possible EXPLANATIONS for the FACT of Evolution. The theory tries to show HOW - natural selection, genetic mutation, adaptive radiation, punctuated equilibrium, and allopatric speciation are some of the big concepts behind that theory. For non-biologists or bio students:
natural selection - differentiated success in reproduction. The organism fittest for survival reproduces most often and eventually dominates the gene pool.
genetic mutation - changes in DNA in the sex cells of organisms due to random mutation, cosmic rays, other factors not yet fully understood. It's important to point out that the only way for a mutation to get passed on if it's in a sex cell, and that sex cell becomes a new organism.
adaptive radiation - one species diversifies rapidly when presented with new opportunities. Darwin's finches are a classic example.
punctuated equilibrium - evolution occurs most rapidly after natural disasters [or after colonization of new empty land] because competition for established or new niches is much less.
allopatric speciation - organisms of the same species in different locations can adapt to different environments and become reproductively isolated [they cannot mate because of physiognomy, behavior, location, etc]. Sympatric speciation [one species becoming several while remaining in the same location] is less common because the population drags all changes back towards the mean.