Suppose you
knew for a fact that killing a particular two-year-old child by firing squad would force the Japanese government to surrender unconditionally, ending the war immediately. Would you do it?
Catholic theology teaches us that you can never commit an evil act in order that good might result from it; you can never kill an innocent person on purpose; and two-year-olds are by definition innocent. So you couldn’t do it.
Now, multiply that action by the thousand of non-military, innocent people killed by the bombs. That doesn’t support dropping the bombs; it makes the analysis worse (because the evil act in question is made more grave by the scale of the offense).
The only way out under Catholic teaching is under the principle of double effect: one may perform a good action even if it is foreseen that a bad effect will arise only if four conditions are met:
*]The act itself must be morally good – it cannot be evil in itself;
*]The only thing that one can intend is the good act – one cannot intend the foreseen bad effect;
*]The good effect cannot arise from the bad effect – otherwise, one would do evil to achieve good; and
*]The unintended but foreseen bad effect cannot be disproportionate to the good being performed.
Invading Japan by conventional means would satisfy these tests, barring specific assumptions made for the purpose of prohibiting the invasion. How does dropping the bomb satisfy them?