Foil
Character Role Analysis
Tom and Chambers
As foils go, these two aren't your average set of opposites. Sure, they're about as different as Ozzy Osbourne and Mr. Rogers. Tom is loud and brash while Chamber is meek and respectful. But what the novel really emphasizes is how differences between who these characters are can be directly traced to differences in how they've been treated. Take a look:
Tom got all the petting, Chambers got none. Tom got all the delicacies, Chambers got mush and milk, and clabber without sugar. In consequence, Tom was a sickly child and Chambers wasn't. Tom was 'fractious,' as Roxy called it, and overbearing; Chambers was meek and docile. (4.5)
As the white kid, Tom is spoiled rotten and, as the slave child, Chambers is treated worse than a family pet. No surprise, each become very different people.
So, in highlighting how completely opposite Tom and Chambers are, Twain wasn't trying to win a contest for Best Foil Ever (although he'd probably be a serious contender). He was making a much bigger point about the effects of slavery and racial prejudice on shaping identities (and you can check out both Tom's and Chambers's character analyses for more on this one).