"... an instantaneous, on-the-spot examination of conscience makes it clear to me that I do intend to kill (not just stop) the aggressor. Should I allow the aggressor to kill me rather than commit a sin?"

If you have enough time to notice that distinction, you have enough time to realize you still need to use lethal defense, but must try not to enjoy it! And if you still want to kill him, the heat of the moment reduces the sin to being venial, not mortal. "Wanting to kill" many times means merely that one understands that solely by an action that kills the person is it possible to totally remove his threat to your life.

There is a reason that ethics is properly taught after a student has studied logic, phil psych, phil of nature, metaphysics and natural theology! It is complex. We have to determine the objective morality of an act, and then, interpret actual responsibility in terms of its modifiers, that is, those elements of passion and circumstance that lessen or eliminate culpability.

"It is unclear to me whether the Church holds that soldiers in a (just) war are licensed to kill (in the same way as an executioner) or are thought to be acting in self-defense."

It can be both. Murder is the deliberate, direct taking of innocent human life without authority. God alone has authority over innocent life. But governments can authorize military defense of a nation which may entail indirect killing of the innocent and direct killing of aggressors. Again, double effect is entailed. Direct hits on military assets may entail unintended side effects that kill civilians. Yes, some of this analysis gets complicated. A military unit behind enemy lines may not be able to take prisoners since it would amount to suicide. Individual soldiers need not determine double effect in each case, since direct destruction of an enemy unit may be justified in the overall war.

"... anyone who finds it necessary to use lethal force to save his or her own life or the lives of others must almost never be acting with the "full consent" required for their actions to be the mortal sin of murder."

Well, if lethal force is needed, it isn't murder anyway. The fact people get confused in their own analysis is not shocking. That is what you have ethicians and moral theologians for. We often find ourselves in confusing situations and, as long as we try to be ethical, we do no subjective wrong, even if an ex post facto analysis reveals unintended objective wrongdoing.

Who said ethics was easy? One must distinguish between the practical science of ethics, which considers the morality of human actions in the abstract, and the practical virtue of prudence which tells us what to do here and now.

No, you are no more allowed to directly intend the death of the Nazi than are you allowed to directly lie to him.

I understand the theory, but how does that work in actual practice? Usually being "good" requires controlling our behavior, not our intentions. Suppose I am attacked on the street or someone breaks into my home and my gut reaction is murderous rage against the aggressor. The only way I can protect myself is by the use of lethal force, and and act of self-defense that inevitably will result in the death of the aggressor is theoretically permissible, but an instantaneous, on-the-spot examination of conscience makes it clear to me that I do intend to kill (not just stop) the aggressor. Should I allow the aggressor to kill me rather than commit a sin?

It is unclear to me whether the Church holds that soldiers in a (just) war are licensed to kill (in the same way as an executioner) or are thought to be acting in self defense. Could you clarify? Is a soldier, who is trained to kill, supposed to be able to use lethal force only if he or she has pure intentions and merely intends to stop the enemy?

The above theorizing aside, anyone who finds it necessary to use lethal force to save his or her own life or the lives of others must almost never be acting with the "full consent" required for their actions to be the mortal sin of murder. So the reasoning about "double effect" and intention seem somewhat unnecessary for the defense of the use of lethal force in self-defense.

No, you are no more allowed to directly intend the death of the Nazi than are you allowed to directly lie to him.

Not too comfortable with intellectual distinctions? You seem neither familiar with the principle of double effect nor with the concept of legitimate mental reservations.

This is why I said earlier: "This is a perfect example of why clear distinctions made in natural law ethics often elude those who have not studied it."

In other words, you can kill a Nazi to defend yourself, but you can't lie to him to defend yourself.

This is a perfect example of why clear distinctions made in natural law ethics often elude those who have not studied it. People very frequently confuse ethics with utilitarianism, wherein a morally good end can be used to justify a morally evil means.

Killing is not identical to murder. Murder is the direct and unauthorized taking of an innocent human life. As such, it is intrinsically evil and never justified. But, when acting in self-defense, one can take actions that simultaneously may end a human life, but are not directly intended. Thus, in shooting an assailant in defense of one's life, this action may entail the shot person dying, but that is not what is directly intended. Rather, the only licit intention must be to remove the threat to one's own life. The key difference can be seen in this: If it is possible to remove the threat to oneself without killing the other person -- even a Nazi, then directly intending to kill would be immoral.

But in the case of lying, if the definition of a lie is fully met, as such, it is intrinsically evil. And since an intrinsically evil act can never be employed to attain an end -- however good the end may be, such an act is never justified.

What confuses people here is that the entire subject of lying is rather difficult to explain -- given the fact that we frequently engage in Sprachspielen or "language games," as Ludwig Wittgenstein so aptly points out. Thus, when someone asks you how you are doing, normal conversation permits one to say, "Just fine," without being expected to mention the toothache you have. It is not considered a lie, since the intent of the question is mainly a formality, not a health inquisition.

I won't go into further detail here, since that could be the topic of an entire essay! Suffice it to say that, if telling a lie is by its very nature evil, then such an evil means can never be justified by the end intended, however good. Such an act would entail a utilitarian justification, which is simply a case of bad ethics.

But, while murder is always killing, not all killing is murder, which is why killing in self-defense can be justified as morally good acts, while real lies cannot be.

how do we know that the Bible is not full of lies.

Because we have no reason to believe it. This is not to defend its truthfulness. It is to assume, as charity demands, that the authors had no intention of deceiving their readers, absent clear evidence of such intention.

I merely posted this to point out that your line of argument is unhelpful because you can't know. If you have no cause to believe that someone is a liar, it's not really helpful to suppose they are a liar. Therefore, I say that your musing on whether God is lying to us for a greater good is an argument that does not really advance any point. You can't prove it, I can't disprove it, so what's really the point?

Great--*priceless*--comment! Thanks!

In "A Taste of Armageddon", Spock says to the guard at the disintegration booth "Sir, there is a multi-legged creature crawling on your shoulder"; there is no such creature -- it is an attempt to put the guard at ease, making him vulnerable to a neck pinch.

In "The Enterprise Incident", Spock tells several lies: That Kirk ordered the Enterprise across the neutral zone on his own authority (the Federation wanted plausible deniability); that Kirk is "not sane" (Spock knew that the insanity was an act); that Spock used the "Vulcan Death Grip" on Kirk (there is no "Vulcan Death Grip", and Kirk is not even dead).

On Organia, Spock tells the Klingons that he is a dealer in kivas, and allows their mind probe machine to discover that his main concern is how he will conduct his business under the Klingon occupation.

And you can't say it is just Spock, with his half-human side:

In Amok Time, T'Pau lies by omission when she does not tell Kirk that he is accepting a fight to the death. (She is a Vulcan and so is surely logical enough to know that outworlders are not familiar with her ceremonies. Plus Spock told her that Kirk did not understand what he was agreeing to.)

In Star Trek VI, Valeris participates in a conspiracy to sabotage the Federation/Klingon peace talks and throughout the movie speaks as if she does not know who the conspirators are. She even participates in the search for the conspirators.

Except for T'Pau (who I think was just being a dick), these lies all advance the greater good, as judged by the Vulcan who is lying. In that respect, the Vulcan view of lies is fairly similar to the Human view: Some lies are ok. Spock has no problem lying to the Romulan Commander in order to aid in stealing equipment from a Romulan ship. I suspect he is using the Nazi analogy here.

The one thing the Vulcans have achieved that Humans have not is a better discipline. They do not routinely lie. They keep this disciplne so well that the rest of the universe actually believes that Vulcans do not lie. This gives them fantastically better credibility when they do.