Another theme is that characters can be a mix of good and evil. Holmes has said she is fascinated by these "shades of gray" in personalities. Her example of this was when Bluestar, a noble and honourable cat, gave up her kits for her own ambitions. Another example she gave of this is how the antagonist Tigerstar, even with all of his faults, is still courageous and fiercely loyal. Similarly, Holmes has also connected the theme to Brambleclaw and how nobody knew whether he was good or evil. A third major theme, often referred to as nature versus nurture, explores whether a character is born the way he or she will be, or if other extrinsic factors shape that. For example, Brambleclaw's father is the evil Tigerstar, but Brambleclaw eventually demonstrates that despite this, he is not evil himself, despite initial suspicion from Clanmates due to his father's legacy. This theme ties into the "shades of gray" theme.