What if I can't wake up. What if I become lucid, and that's the final step to entering that world. What if you see it, and it's too horrible, and it makes you hate me.

Not rational fears, unlike the issue of his mental health, but then again: these are not rational times. Strange happenings are ordinary. Clark is not human, and Bruce is having visions. Resurrecting a man using a blip in time travel and alien technology from two different worlds is not actually any less outlandish than another timeline trying to supersede its way into Bruce's reality.

Also, softly, "I have no fucking idea."