Modeling Good and Evil, Part I
In this model, there are a number of individuals each with their own moral "compass". There is no preferred individual, that is, no one agent's moral sense is intrinsically better (i.e. more moral) than any other's. There is also no external standard of morality to which individual agents ought to conform.
One aspect of this model that should be agreed on is that each agent's moral compass points in a different direction. Pick any contentious subject and it's clear that there is no moral consensus. As the number of agents increases, there will be cases where some compasses point in the same general direction, but whether or not this is meaningful will be discussed later.
Two adherents of this model are the physicist Stephen Weinberg and the philosopher Jean Paul Sarte. Weinberg wrote:We shall find beauty in the final laws of nature, [but] we will find no special status for life or intelligence. A fortiori, we will find no standards of value or morality.
The existentialist, on the contrary, finds it extremely embarrassing that God does not exist, for there disappears with Him all possibility of finding values in an intelligible heaven. There can no longer be any good a priori, since there is no infinite and perfect consciousness to think it. It is nowhere written that “the good” exists, that one must be honest or must not lie, since we are now upon the plane where there are only men. Dostoevsky once wrote did God did not exist, everything would be permitted”; and that, for existentialism, is the starting point. Everything is indeed permitted if God does not exist, and man is in consequence forlorn, for he cannot find anything to depend upon either within or outside himself.
The next model is the same as model 1, with the addition of an external moral compass:
There is no universal agreement on where this external source comes from. One adherent of this model is Michael Shermer:
... I think there are provisional moral truths that exist whether there’s a God or not. ... That is to say I think it really exists, a real, moral standard like that.
Note the violent disagreement between Shermer and Sarte. Later, we will explore whether or not we can determine if either of them are right.
But first, part two will present two more models.
 Dreams of a Final Theory: The Search for the Fundamental Laws of Nature.
 Existentialism Is a Humanism
 Greg Koukl and Michael Shermer at the End of the Decade of the New Atheists