Chapter 6 begins with a reporter trying to find out whatever he can about Gatsby. How has Gatsby become who he is? What are some of the stories told about him, and where do they come from? What does Gatsby mean when he insists that he can "repeat the past"?

In chapter six, Nick Carraway tells the story of Jay Gatsby's past. Jay Gatsby was born into a poor farming family in North Dakota and was named James Gatz. He was remarkably self-disciplined and was determined to better himself. James had dreams of one day occupying the upper class of society and living like a wealthy aristocrat. After dropping out of college, James traveled to Lake Superior to dig for clams and fish for salmon. One day, James Gatz met a copper tycoon named Dan Cody on Lake Superior and introduced himself as Jay Gatsby. Cody offered him a job, and Gatsby spent the next five years sailing around the world with Dan Cody on his luxurious yacht. Shortly after Dan Cody died, Gatsby met and fell in love with Daisy Fay before he left the United States to fight overseas in WWI. When Gatsby returned from Europe, he met the unscrupulous, shady Meyer Wolfsheim and entered the illegal bootlegging industry with him. Gatsby managed to amass a fortune working as Meyer's business partner and earned enough money to purchase a mansion in the West Egg across from Daisy's estate. Essentially, Jay Gatsby attains his wealth through illegal means but nonetheless achieves the American Dream.
The first rumor about Jay Gatsby that Nick hears takes place during Myrtle and Tom's small party in the city. Myrtle's sister, Catherine, tells Nick that she heard that Jay Gatsby was the nephew or cousin of Kaiser Wilhelm. When Nick attends his first party at Gatsby's lavish mansion, a woman mentions that Gatsby was a German spy during the war, while another woman insists that he killed a man. Jordan Baker even tells Nick that she doesn't believe that Jay Gatsby is an Oxford man. At the beginning of chapter four, Nick overhears a woman say that Gatsby is a bootlegger who killed a man that found out he was the nephew of von Hindenburg.
Towards the end of chapter six, Nick mentions that Gatsby wanted Daisy to immediately divorce Tom and move away with him, which is an entirely unreasonable request. When Nick says that Gatsby cannot repeat the past, Gatsby responds by saying,

Can’t repeat the past? [. . .] Why of course you can!(Fitzgerald, 118)

Gatsby desperately desires to be with Daisy again and wants to repeat their relationship, which took place five years ago. However, Daisy has moved on with her life, is married to Tom Buchanan, and has a child with him. The situation is completely different the second time around, but Gatsby holds onto the false hope that he can repeat the past. He simply desires to have Daisy all to himself and naïvely believes that she should leave her life behind to be with him. Tragically, Gatsby learns that he cannot repeat the past and that his dreams of being with Daisy are unrealistic.