Casey Cathy I believe is what today we call a sociopath; no capacity for remorse. Steinbeck speaks of her lacking something that makes the rest of us human, perhaps the ability to feel love. she only begins to sense she is missing something at the end, when she goes to watch Aaron in the church. I think she, finally, realizes others have something extra which she does not, but her lack of understanding only leads her to anger and more cruelty. Does her final cruel treatment of Aaron prove she was born evil, lashing out at the one person the reader might have wondered if she had even the smallest of care for? It does seem she is lashing out through her frustration of missing that ''something" which gives the rest of us our humanity. which is to say, I think there is nothing but evil in Cathy. I too have known a 'Cathy' AND was just as blind to it as Adam was until it was incredibly blatant (which came soon, he did not have Cathy's intelligence). and by the way, did anyone else desperately wish they had a Lee in their life from reading this book as much as I did?
Mike Pentola I think she was born evil, and kind of contrasts the more typical type of humans made up of both good and bad, who populate most of the rest of the novel. Aaron, Lee, Samuel and Adam are all mostly good, though not without their weaknesses (especially Adam), and Cal seems to be torn often between pure good and pure evil, the pure evil inherited from Cathy.
Sarah I think, like all humans, Cathy was born evil. However, I think that her evil and her sins were more tangible than others', if only because of Steinbeck's revealing narration—she was subtle and manipulative, resorting only to outright violence when backed into a corner. In reality, there are likely Cathys all around us. We are all like Cathy in certain ways, ruthlessly dedicated to fulfilling our desires.