A morality (moral code) rests on its system of values. A discussion of moral truth refers to the aetiology of these values, and how universally applicable and fixed they are (and to what frame of reference).
The Nietzschean attack on utilitarianism as the odious 'herd-morality' might describe good and evil in the following way:
- the good man knows and abides by the 'right' system of values (moral)
- the bad man is one whose values are skewed, and who consequently 'sins' by acting according to these misguided values
This explanation has the advantage of fitting in perfectly with the Christian morality, if one includes the existence of a good and powerful God. God set down our values on tablets of stone: the heathens need to be preached at, and everyone else needs to be - preached at too. It is in line with the Platonic stance of the 'bad man sins involuntarily through ignorance'. Teach everyone the good Christian way, and all will be well, for the good Christian way is, coincidentally, the socially-cohesive way. (With only a little twist, we can incorporate the Superman. The good and the bad are 'small people'. The Superman is neither: he is beyond good and evil, for he creates his own values.)
Could it be that, in fact, the bad man knows the difference between 'right' and 'wrong'? i.e. they have the same values as all of us but willingly ignore them? That makes no sense. If a murderer placed the same value on human life as a pacifist, he wouldn't murder. Instead, it must be that they have a skewed or vastly differently-organised set of values. No one would willingly act out selfishly if they valued others as highly as themselves. Bad = a different set of values. That is what the justice system of punishments to deter is all about: if they can't classically condition or indoctrinate people into the herd-convenience of neminem laede, then they will artificially weight the criminal/bad man's value system so as to align with everyone else's: by bolstering the options of not harming others by attaching negativity to 'bad' actions (prison etc.), then, everyone's moral mechanism can be balanced and weighted to accord with social harmony.
However, if you would rather have slightly more ultimate and intrinsic grounds for your way of life, you need a God. A big, badass, loving all-powerful God who'll tell you just what's what. The Judaeo-Christian God is the playground bully of the gods ('though shalt not worship any other piddly gods before me' etc.) - definitely a good one to go for. He'll provide the absolute framework for our ethics to rest upon. Without which, this Christian framework is reduced to a social convenience, a contract. But a contract with no escape clause. One cannot back out and exempt oneself from the benefits and restraining protection of civilised justice and go on killing sprees, even if one chooses. The herd will round upon aggressive sheep for the benefit of the other sheep, but it will similarly attack stray sheep, those who scorn the protection of the herd but are still denied the freedom of the individual lion. This is all that we have if God is dead. With God, then we should be 'good' because God says so. This is why Nietzsche's statement 'God is dead' is so earth-shattering - it literally grabbed the rug from under religion's feet, upturned good and evil and destroyed the fundamental world order upon which all Western civilisation had been built.
The problem for us now, is that it seems impossible to believe that the God of the bible exists (he's so laughably humanly petty), yet I'm unable to actually BELIEVE he doesn't. Because atheism requires just as much faith as religion.