He hadn't expected the Master to be impressed or particularly affected by his words, so he was unbothered by the Master's reaction. "You're wrong," he said softly. "People cannot leave this place. They've tried. It does not work. The Doctor has tried." And, considering the improbable bullshit the Doctor could manage, he very much doubted that if he couldn't leave, the Master could. "So there's no way that you can get to Telos." Now that the initial panic had passed, logic was setting in. He was comfortable with logic. It was better than focusing on the minute possibility that the Master would somehow succeed.
It took everything in him not to panic at the sight on the screen. He could hear Tosh in his head, telling him there were millions of ways to tamper with a video feed. That the Master hadn't proven anything with that little show. Still, it was hard to believe it. He got to his feet, even though his hands were still shaking slightly and he was a little too pale. "That doesn't prove anything," he said, though he was having trouble believing it, "other than that you know how to work a video screen. That video could be of any time, any place. It certainly doesn't prove that's what's actually outside." He felt a little better now. Logic really did help.