My point here is that the
“Prohibition for Murder” cannot be an “Absolute Morality”…
Practically these are some grounds for killing people:
so is there a specific moral law that will work absolutely all the time?
Yes. Murder is bad. You still don’t distinguish between murder and killing (and by your examples, think that killing is justified when it is not). What you proposed were grounds for killing. If they were truly grounds for killing, which some aren’t, then such killings would not be murder. A better direction for you to come from is “what is murder?”
The answer you would probably get is “killing that is not justified.” The next question would be “what justifies killing?” And that would be a long and complicated answer, but the fact that it would be long and complicated does not mean that it does not exist.
But I can give you a partial answer, one thing that is certainly and always true. It is not supposed to be a complete answer, mind you, only a (unless I mess up) loophole free absolute statement. And if I accidentally leave off some clause and leave a loophole, then the statement will be able to be expanded to close it by adding “and when X loophole doesn’t apply”.
Here we go: “It is always wrong to kill someone who you have never seen or heard of before, who is not noticeably doing anything at all other than just sitting there and who will not to your knowledge ever cause anything bad to happen by just sitting there, who’s future plans you have no idea about, who no one has instructed you to kill or even mentioned to you at all in any way, who you don’t think you are justified in killing, and who you have absolutely no motivation to kill whatsoever except perhaps a desire that did not spring from any source that you have been able to identify at all beyond a sudden feeling of ‘I want to kill that guy’.”
I think I’ve closed all loopholes. That should be an absolute statement. My point is, every time you point out an “exception” to a rule, you are not in fact showing that there is no rule, only that the rule needed to be stated more clearly in order to be precise. But rules can be complicated. Which is why we say that murder is unjustified killing, give a few guidelines to determine when killing is justified, and say figure it out yourself and avoid killing at all when possible, because unjustified killing is really bad and we don’t want to do it by accident.
Even when there is an absolute rule, it is not always easy or even necessary to state it with absolute clarity - not easy because there are a wide range of possible actions, not necessary because we’re not stupid and can generally get by by reasoning off a few principles. More precise statements are good because they narrow down the amount of ways you could mess up in your reasoning, but there is only so much time in the world and not all of it can be used to explain exactly under what conditions you can give someone a dirty look.