Looking through Shakespeare's Julius Caesar, the fate of the people shows to be greater than their freewill. The fate of the people in the story controls their life more than they control their life. Most of them live their lives based on omens, soothsayers' predictions, signs from dreams, and etc. If these signs say an event is going to happen, then the event is going to happen.
For example, in the story, a soothsayer warns Caesar to "beware the ides of March". As the story turns out, Caesar dies on March fifteenth, the ides of March.
Another example is Calphurnia's dreams. All the events happening in her dream, such as a lioness whelping in the streets, suggest to her that something dangerous is going to happen to Caesar. As fate wanted the situation to happen, something dangerous did happen to Caesar.
Many omens throughout the book suggest the fate of people. An omen to Cassius in the battle of Philippi suggests the defeat of him and all his armies. Expecting defeat, Cassius and Brutus say their farewells to each other. As the omen suggested, they were defeated in the battle.
With these examples, I found the theme of Julius Caesar to show the audience nothing can be done to control fate. What is going to happen will happen no matter what.