Trivia: Stay after the credits. There's an additional scene where John goes to visit Chas' grave and leaves a lighter, then as he's walking away you see Chas with wings and he flies up into the sky. (01:54:40)
Trivia: Jay and Silent Bob (from Kevin Smith's films) get a mention during the movie. When talking about sidekicks, three are mentioned, the first two by name, and the third is a description of Jay and Silent Bob. (00:19:25)
Trivia: The name of the Mexican guy who found the Spear of Destiny is Manuel. (It's revealed in the opening scene, when his fellow calls after him in Spanish.) Manuel is the Spanish form if Immanuel, the name of the Messiah according to the Book of Isaiah. Occult interpretations of the Bible commonly claim that Immanuel will be the name of Antichrist.
Answer: Sin for a good reason is still sin, and as Gabriel says earlier, you can't buy your way into Heaven. Real Catholic dogma, however, doesn't hold the mentally ill as condemned for committing suicide.
Greg Dwyer
Except Isabel wasn't mentally ill. She saw angels and demons just like Constantine did. It was her parents who believed she was mentally ill.
While suicide is a mortal sin, it's shown later (as in major plot point) that sacrificing yourself to save the world is a redeeming act.
Yes, but Constantine also said "My parents were normal. They did what most parents would do. They made it worse. You think you're crazy long enough, you find a way out" which could relate to Isabel losing her sanity in a way as well because of her family and how they saw her. The whole Isabel's sacrifice is added by the novelization but the movie is ambiguous about the suicide.
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Except Isabel wasn't mentally ill. She saw half breeds just like John did.
Sacrificing yourself for others isn't a sin.