What is the theme in Beyond the Horizon by Eugene O'Neill?

For both Robert and Andy, dreams are also responsibilities. Robert has signed up with his uncle, Captain Scott, to work on the sea voyage. When he backs out, he neglects his responsibility, a fact that irks Captain Scott, who has gone to great lengths to accommodate Robert. Says Scott, "Ain't I made all arrangements with the owners and stocked up with some special grub all on Robert's account?" Meanwhile, Andy has trained since he was a boy to manage the Mayo farm, and when he backs out of this responsibility, his father challenges him on it: "The farm is your'n as well as mine . . . and what you're sayin' you intend doin' is just skulking out o' your rightful responsibility."