(68) Why he who knows all things asks the fratricide: “Where is thy brother Abel?” (#Ge 4:10). He puts this question to him because he wishes the man to confess voluntarily and spontaneously, of his own accord, so that he may not imagine that every thing is done out of necessity; for he who had slain another through necessity, would have confessed unwillingly, as having done the deed unwillingly; since that which does not depend upon ourselves does not deserve accusation; but the man who has done wrong intentionally denies it; for those who do wrong are liable to repentance. Therefore, he has interwoven this principle in all parts of his legislation, because the Deity himself is never the cause of evil.
(69) Why he who had slain his brother makes answer as if he were replying to a man; and says, “I do not know: am I my brother’s keeper?” (#Ge 4:9). It is the opinion of an atheist to think that the eye of God does not penetrate through every thing, and behold all things at the same time; piercing not only through what is visible, but also through every thing which lurks in the deepest and bottomless unfathomable abysses. Suppose a person said to him, “How can you be ignorant where your brother is, and how is it that you do not know that, when as yet he is one out of the only four human beings which exist in the world? He being one with both his parents, and you his only brother.” To this question the reply made is: “I am not my brother’s keeper.” O what a beautiful apology! And whose keeper and protector ought you to have been, rather than your brother’s? But if you have excited your diligence to give effect to violence, and injury, and fraud, and homicide, which are the foulest and most abominable of actions, why did you consider the safety of your brother a secondary object?”