How does Arthur Miller construct contrasting characters (Abigail and Elizabeth) to convey his central concerns?

Abigail and Elizabeth are almost character foils for each other. Where Elizabeth is virtuous and principled Abigail is reckless and irresponsible. The chaos that Abigail unleashes upon the village is enough to destroy even the most righteous like Elizabeth Proctor. In the end this is one of Miller's central themes. The hysteria and darkness of human nature overcomes even the best of human nature.