I believe in God, in science, in... Sunday supper.

From CSI Season 2 Episode 6.

Gil Grissom: We both have jobs that begin after the crime.
Father Powell: After the sin.
Gil Grissom: Some people would call that a career in futility.
Father Powell: Some call it a vocation.

Gil Grissom: A hundred years ago, we didn't have the technology for fingerprints. Fifteen years ago, we didn't have DNA. Hopefully one day, we'll have foolproof means by which to put the right man in jail in this case.
Father Powell: Someday we won't need jails.

Father Powell: I celebrate mass every Thursday night, 7 o' clock.
Gil Grissom: Thank you... but... no.
Father Powell: You don't believe?
Gil Grissom: In religion. I believe in God, in science, in... Sunday supper. I don't believe in rules that tell me how I should live.
Father Powell: Even if they're handed down by God?
Gil Grissom: How many crusades were fought in the name of God? How many people died because of... someone's religion.
Father Powell: Fanaticism, not religion.
Gil Grissom: Semantics. They're still dead. ... I'm sorry about Ben, Father.

[Ben is the character who was arrested for murder of two men, but later declared innocent.]

Father Powell: You still suffer like a Catholic. ... Light bulb goes out, other people fix it, get a new one. Light bulb goes out for the Catholic, he stands in the dark and says "What did I do wrong?"
Gil Grissom: That guilt's not in me anymore.