Just as there are physical monsters, can there not be mental or psychic monsters born? The face and body may be perfect, but if a twisted gene or malformed egg can produce physical monsters, may not the same process produce a malformed soul?
Monsters are variations from the accepted normal to a greater or a less degree. As a child may be born without an arm, so one may be born without kindness or the potential of conscience. A man who loses his arms in an accident has a great struggle to adjust himself to the lack, but one born without arms suffers only from people who find him strange. Having never had arms, he cannot miss them. To a monster the norm must seem monstrous, since everyone is normal to himself. To the inner monster it must be even more obscure, since he has no visible thing to compare with others. To a man born without conscience, a soul-stricken man must seem ridiculous. To a criminal, honesty is foolish. You must not forget that a monster is only a variation, and that to a monster the norm is monstrous.
"East of Eden"