Morality (from the Latin moralitas "manner, character, proper behavior") is the differentiation of intentions, decisions, and actions between those that are "good" (or right) and those that are "bad" (or wrong). The philosophy of morality is ethics. A moral code is a system of morality (according to a particular philosophy, religion, culture, etc.) and a moral is any one practice or teaching within a moral code. Morality may also be specifically synonymous with "goodness" or "rightness." Immorality is the active opposition to morality (i.e. opposition to that which is good or right), while amorality is variously defined as an unawareness of, indifference toward, or disbelief in any set of moral standards or principles.[1][2][3][4] An example of a moral code is the Golden Rule which states that, "One should treat others as one would like others to treat oneself."
It does seem as though morality is interdependent with ones upbringing.
For instance, is the marriage of a 30 year old man and a 14 year old girl immoral?
In some cultures the answer would be 'yes' and in others 'no'.
So the marriage is both moral and immoral depending on ones personal set of moral codes and values which are developed over time.
Is killing someone moral or immoral? Depends on the circumstances, right?
But it also depends on who is sitting in judgement.
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Going back to the OP, the reason Adam's sin wasn't atoned for is because Adam isn't a real person.