Dr. Ferris is a member, along with Wesley and James, of what we like to call the trio of evil. While James embodies evil business and Wesley evil politics, Ferris is here to represent evil science. Among the three of them, we get a good idea of the looters' ideology, the types of people in power, and the impact they have on national life.
In terms of influence, Ferris might the most powerful of the three. He's also one of the most outspokenly cynical of the looters. He often cuts through all the ideological rhetoric and gets to the heart of the matter: he has great contempt for people and is basically in it for power. Oddly enough, one of his most revealing scenes occurs not with his fellow looters but with his nemesis Hank Rearden:
"We're after power and we mean it. You fellows were pikers, but we know the real trick, and you'd better get wise to it. There's no way to rule innocent men. The only power any government has is the power to crack down on criminals. Well, when there aren't enough criminals, one makes them...you create a nation of lawbreakers – and then you cash in on guilt. Now that's the system, Mr. Rearden." (220.127.116.11)
This is probably the best statement of the looters' government system in the entire novel. Ferris comes right out and says exactly what the looters are doing and what they hope to achieve: power. What's interesting is Ferris's tone here. He speaks to Hank in this scene as if Hank is a total idiot who is hopelessly behind the times. Ferris actually relishes this type of criminal system and doesn't understand why a "smart" man like Hank won't get with the program.
This isn't to say that Ferris never uses ideology, though. He often fires off the same hollow phrases and ideals that people like James Taggart embrace. But while James clings to such phrases as a life-preserver, Ferris uses them as a way to mock those around him. Here's an example of a scene with Dr. Stadler:
Dr. Ferris did nothing, he merely looked at Dr. Stadler calmly; but the calm gave him an air that was almost patronizing. "Now, you see, Dr. Stadler, you're speaking as if this book were addressed to a thinking audience. If it were, one would have to be concerned with such matters as accuracy, validity, logic, and the prestige of science. But it isn't. It's addressed to the public. And you have always been the first to believe that the public does not think. He paused but Dr. Stadler said nothing. (18.104.22.168)
Ferris here throws Stadler's beliefs back in his face, showing him the logical extremes to which Stadler's contempt of the "public" can be taken.
In the end, Ferris uses his power and influence over the country's science and technology to create weapons and ways of terrorizing people into submission. He's the character who pushes for Galt's torture. Ferris shows us what some men of intelligence and ability can become in a system like the looters'.