Principle of double effect

In ethics, theologians cite the principle of double effect that states the necessary conditions to be met when one's action is considered morally right even thought it accompanies evil effect in some way. They are:

• the act itself is good or morally neutral
• the good effect is not brought by gaining the evil effect
• the good effect is intended and the evil effect is not intended but only permitted
• the good effect outweighs the evil effect, or at least they are comparable.