Silas Marner? Dunstan Cass? Fate?
This one's a little tricky. In some ways, Silas is his own worst enemy. His own shyness, lack of experience, and inability to trust keep him from integrating into Raveloe. But you could also say that Dustan is the antagonist, since he's the one who (1) produces Eppie by convincing Godfrey to marry Molly; and (2) steals Silas's money. And at the same time, fate seems to be working against Silas as much as anything else. So, who or what is the primary antagonist in Silas Marner? What is keeping Silas from achieving his goals—and, if he doesn't have any goals, then what does the antagonist even do?