In order for God to be just in punishing Cain, Cain had to know that murder was wrong. He even had to know murder was punishable by death as he feared for his life.
Torah, given in Eden, was/is for all mankind.
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Tag: Abel
How did they know? Abel.
There are numerous references to Torah commands throughout Genesis that were supposedly first give at Mt. Sinai. How did they know?
Either, Abel was just lucky, OR the full Torah was given to all mankind in Eden and pre-existed the Fall?
11:3 Restoration 