Ferneze is the Christian Governor of Malta, and father to the ill-fated Lodowick.In big picture terms, he bookends the main action of play: he's both the guy who gets the ball rolling (his confiscation of Barabas's wealth is what sets everything in motion) and the one who eventually puts an end to all the mayhem (he betrays Barabas at the last minute, resulting in Barabas's death).
You probably had some trouble figuring out how to feel about Ferneze. On one hand, he's Barabas's main enemy, and since Barabas is (at least by time he kills Lodowick and Matthias) an indisputably terrible person, you kind of feel like you should be on Ferneze's side.
But hold up, Shmoopers. Can you really say Ferneze's a good guy? Even though Barabas is introduced as the play's "Machiavel," Ferneze's no pussycat himself. Let's take a look at some of Machiavelli's Greatest Hits:
Plain English: It's ok to break promises if keeping them is disadvantageous.
Ferneze is clearly on board with this one: he swears that he'll have ten years of tribute money ready for Calymath by the end of the month, but the minute the Spanish navy offers to help him out (and therefore the "occasion"—Malta's total military vulnerability—disappears) he goes back on his promise and tells Calymath to suit up for a siege.
Plain English: You'd better look religious, even if you're not.
Okay, this one's a little tricky, because it's tough to gauge Ferneze's real religious commitment. Bottom line, though, is that Ferneze is definitely prepared to publically espouse Christian values (and, more importantly, Christian prejudices) to get what he wants. People die left and right in the play, but one of the nastiest scenes is still that first bit where Ferneze is telling everyone how righteous he's being by confiscating the Jews' wealth.
He, of course, just needs their money because he's gotten himself into a bad situation with the Turks, but the way he tells it you'd think God had personally asked Ferneze to take Barabas's property. In Barabas's words, Ferneze "preaches the Jews out of their possessions" (1.2.11).
Plain English: The ends justify the means.
You can get behind Ferneze's "good end"—he's pretty consistently pushing for a stable and peaceful Malta, whereas Barabas seems to just want to stay alive while killing off everyone else. That said, think of what he does to get there: he shamelessly exploits the minority Jewish population, breaks his promise to Calymath, betrays Barabas, and then ransoms Calymath to extort the Turkish Sultan.
Ultimately, Ferneze does indeed regain control of Malta, finish off Barabas, and make a pretty solid plan to rebuild the city. That said, when you look at the way he accomplishes all that, he ends up looking pretty morally dubious?