Shmoop doesn't like to put words in anyone's mouths, but if we had to ask Matt what he's learned after all his harrowing adventures, we'd like to think he'd say this: you are what you do. This is something that Tam Lin tries to hammer into Matt, who struggles to live with the knowledge that his genetic twin is an evil wacko. In order to overcome this unfortunate heritage, Matt has to make his actions and choices count. Other characters, too, are also largely defined by their actions. We know Tom is not a good guy because he never does good things. Celia and Tam Lin, however, both stand up to El Patrón, and for that, we know they're heroes.
Contrary to Juliet's belief that "A rose/ by any other name would smell as sweet,"names matter in The House of the Scorpion. Many of our characters have names that are not their own. Tom, for example, lives a lie as an Alacrán, even though he's really an illegitimate MacGregor. Matt, too, lives with a name that isn't entirely his own, and later makes up a new name to protect his life. El Patrón basically no longer even needs a name, despite the fact that his last name still carries enormous power in Opium. The eejits working the Alacrán estate have all lost their names, along with their sense of self. Some names serve as shout-outs or descriptions, too (see the "Character" pages of Tam Lin and Fidelito). Overall, names clue us into a person's status, or lack thereof, in the world of the novel.