This double vision applies to people places and event. Explain its significance and how this is true. (use references to the novel to support your idea)
As the posts above have suggested, this twin view of Gatsby's world (or the world of the rich) is intentional.
Those on the outside who read the culture columns or the gossip pages are made to believe that the rich are somehow evolved, refined, or simply better than people less wealthy. But this is a matter of glamour in the most literal sense. Glamour, as a term, refers to the trick of appearances that dazzles and fools the eye.
Those on the inside are not fooled and are not glamorous in the way we would usually use the term. They are petty, jealous, and corrupt. That's not to say they are bad people, but they are no better than people who are less wealthy. They're just like everyone else, struggling to be happy.
That's the whole idea. The story is told through Nick's eyes, who at first is blinded by all the glamour and glitz. As time goes by, Nick becomes more jaded as he tries to hold on to his own values. He finally sees Daisy and her world for what it is: corruption and a cancer all dressed up. If one gets caught up in it, it eats you from the inside out. Nick makes the right decision after Gatsby is murdered in his own backyard to go back home to the west where people actually know how to behave.
This double vision is exactly what Fitzgerald wants us to see. He is pointing out the corruption and lies and deceit that spawns from the rich who live in the East Egg. From the beginning chapter, Nick sees everything through the eyes of a naive westerner. He is amazed at not only the size of Daisy's house, but of the colors and the sweeping look of it all. It's so glamorous to him.
"We walked through a high hallway into a bright rosy-colored space, fragilely bound into the house by French windows ta either end. The windows were ajar and gleaming white against the fresh grass outside that seemed to grow a little way into the house. A breeze blew through the room, blew curtains in at one end and out the other like pale flags, twisting them up toward the frosted wedding cake of the ceiling--and then rippled over the wine-colored rug, making a shadow on it as wind does on the sea."
Fitzgerald shows us how money changes people when he describes Myrtle when she changes dresses at her city apartment. This is perhaps where Nick begins to see Tom and Myrtle and even Daisy for who they truly are. Later then he witnesses Tom Breaking her nose.
"With the influence of the dress her personality had also undergone a change. The intense vitality that had been so remarkable in the garage was converted into impressive hauteur. Her laughter, her gestures, her assertions become more violently affected moment by moment..."