Duality, two sides to the same topic or issue, certainly runs all throughout John Guare's play Six Degrees of Separation and underscores the themes of racism and class distinctions.
One duality that exists is rich vs. poor. In the story, the lead character Paul, who is also poor, gets his MIT friend Trent Conway to help him learn the manners and language of the upper class in order to con them out of their possessions. We particularly see part of the education Trent instilled in Paul in the following passage:
This is the way you must speak. Hear my accent. Hear my voice. Never say you're going horse back riding. You say You're going riding. And don't say couch. Say sofa. And you say Bodd-ill. It's bottle. Say bottle of beer. (p. 43)
Since the author draws such a marked distinction between how rich and poor people speak and behave, we can easily see how he is using this duality to underscore the theme of class distinctions.
A second duality that exists concerns the educated vs. the uneducated. Paul only has a high school degree, whereas his friend Trent and the people he is trying to con are either being educated or have degrees at Ivy League schools. The irony is that Paul is using his own private education with his friend Trent to learn how to rob the more educated, whereas he actually could be earning a legitimate education to become wealthy himself one day. Again, this duality also underscores the theme of class distinctions.