As HellCat and some others have said, Hawking controls the computer using a finger. I also saw a news story on TV where they said they are also setting up an eye controlled system for him in case he loses the ability to move his finger, as it's one of the few things he can still move.

But, I think that when this thread started, there was a different question. Even if Hawking is doing what he wants, he still has caretakers, and they can influence him. Just like the Chief of Staff can influence the President greatly by allowing him to hear various things, Hawking's caretakers could influence who gets to meet with him and such.

As far as those who say he is not that smart... that's a tough question. I believe he is extremely intelligent, but he is not liked by some other physicists. Part of the problem is that he is a popularizer, he writes many things for a public audience, and many academics feel that popularizers are sellouts, that they are watering down their real research to make money. There is something to that, but I also think that it's good to improve public knowledge of these issues, so some amount of popularization is a good thing. If Hawking wants to spend his time popularizing, telling the public about all the cool stuff he and other physicists talk about in a way they can understand, more power to him.

idk who or even what controls the thoughts of that great man. What I do know though is that Hawking particles exsist and space time is screwy and can be "danced" with point of view and your own personal "Bounce". Hawkings is the shiznit!!!