In Fitzgerald's The Great Gatsby, what is Nick's meaning when he balances Gatsby's supposed corruption against his incorruptible dream?
That line is delivered in Chapter 8, as Nick is waving good-bye to Gatsby on the morning after the disastrous Sunday afternoon trip to the city. It is the last time he will see Gatsby alive. Gatsby has just told Nick the truth about who he is (originally James Gatz of North Dakota) and of how he first fell in love with Daisy.
Nick calls Gatsby "corrupt" because he is a pretender. His money is made from selling "grain alcohol over the counter" of a string of drugstores (this is during Prohibition). This would be shocking to the guests at his parties, who had "guessed at his corruption," that is, guessed that his money was not honestly earned or inherited, though Gatsby is passing himself off as upper-class.
Gatsby has deceived Daisy as well. When they first met, he did not intend to fall in love with her, pursue her, and marry her. He was a poor boy who was besotted with the kind of life she lived (her house, for example), and wanted to belong to that world. He knew that he could never do this, so he intended just to seduce Daisy and then get away before she realized that he had deceived her. But they accidentally fell in love. Then Gatsby was sent away to the war, and while he was gone, Daisy married Tom.
Gatsby has spent the last four years trying to become what Daisy thought he was, so that he can win her back "honestly." And this is his incorruptible dream: that he can actually turn himself into someone else ... into his "Platonic ideal" of himself, as Nick calls it. James Gatz can turn into Jay Gatsby, and he can go back and re-create the past: he can be Jay Gatsby, truly rich, truly worthy of Daisy, and he and Daisy can fall in love as they did five years ago, but get married this time. Gatsby's incorruptible dream is the whole scene: himself, rich and sophisticated, in love with Daisy, and Daisy in love with him. Of course, it is not possible to achieve this, but Nick sees and, in a sense, respects Gatsby's dream.