According to melanie klein, notions of good and bad, and right and wrong, come from:

an infant's interactions with his or her mother's breast during the oral stage

Explanation:

According to Klein the mood that the mothers in whenever they fed their children could influenced their emotional state that can determine their behavior in the future. She stated that when the mothers Brest fed their children lovingly and with care, the children could sense that and they will grow up with the exact same behavior. They will be less violent and more sociable.