[Sebastian shakes his head - if it's meant as an answer or just an attempt to clear his own head... well, he probably doesn't know that himself. At least he doesn't seem to take any notice of Ciel's embarrassment.]
Desired, [he tries to clarify, putting some emphasis on the word. Desired, not "was thinking".] It's... the soul. I can only infer thoughts from that.
Young master, it is... [and we're back to giggling: he's never going to stop finding everything incredibly funny, it seems] utterly entertaining to attempt to understand you.