I love that fact that he thought Daniel was a hallucination at first... How often does Jack have hallucinations, anyhow?

But mostly I love how Jack changes the moment he starts believing in the possibility of escape no matter how improbable that escape may be.

IMO, Daniel so wants Jack to ascend that he convinces him that there is no possibility of escape, only to be faced with the fact that Jack would choose death first (having just been so badly burned by the last "helpful" alien thing that was offered to save his life).

But by that time it's too late: Jack believed him and is, basically, giving up.

Still, the moment he believes again -- he's a totally different person.

I love that.