SCOTT: Locked on to something. Does that appear human to you, Mister Spock?
SPOCK: Fascinating. For a moment, it appeared almost mineral. Like living rock with heavy fore claws. It’s settling down now to completely human readings.
SCOTT: We can beam it aboard anytime now, sir.
[...]
(Kirk, Lincoln, Spock and security leave)
MCCOY: Just what was it you locked onto before you beamed him aboard?
SCOTT: You heard Mister Spock yourself. Mineral he called it, like living rock.
MCCOY: And that became Lincoln?
SCOTT: I couldn't tell. It may have been another figure down there standing by. What do you make of it?
MCCOY: I'm not quite sure.
[...]
CHEKOV: The deterioration in the shielding has stopped and is reversing itself. I have no explanation.
KIRK: Thank you, Mister Chekov. Mister Spock, any explanation?
SPOCK: Conjecture, Captain, rather than explanation.
KIRK: Well?
SPOCK: It would seem that we were held in the power of creatures able to control matter and to rearrange molecules in whatever fashion was desired. So they were able to create images of Surak and Lincoln after scanning our minds and using their fellow creatures as source matter.
KIRK: They seemed so real. And to me, especially Mister Lincoln. I feel I actually met Lincoln.
SPOCK: Yes, and Surak. Perhaps in a sense they were real, Captain. Since they were created out of our own thoughts, how could they be anything but what we expected them to be?