Being firmly in the deontological camp (rationalist ethics) myself, though, I would recommend you check out Kant, Nagel, and the many advocates of the non-aggression principle (pick your author). I believe our intrinsic notions of morality are mostly deontological, which makes some sense as non-aggression and other subforms of the school allow a person to act morally with local information, rather than requiring global knowledge for every act, as much of utilitarianism requires in the final analysis.
If you would kill one innocent person because you thought that action might save five innocent people, though, then you are probably (and unfortunately) a utilitarian. Do consider both sides though.