- the end of having clean water in a poor country justifies the means of building a water well.
--a good end (clean water) can justify a good - or neutral - means (digging a well).
- the end of getting information from a terrorist never justifies the means of torture
--a good end (getting information) cannot justify the evil means (torture)
This kind of philosophical precision is necessary for good Christians to think through, because of the kind of philosophies that have entered into our culture and way of reasoning. Most citizens would probably justify their positions on torture or other evil acts by the ends. The root of such thinking comes from utilitarianism (the morality of an act is based on the utility - or ability - of it to bring happiness and pleasure) and consequentalism (the consequences of an act make it moral or not). Both are philosophies that are self-serving, non-Christian, and far from loving. A good round-up of both can be found here.
Do the ends justify the means?
Not if they are evil means or ends.
"Men do not differ much about what things they will call evils; they differ enormously about what evils they will call excusable." - G.K. Chesterton