What is Ahab?

I think the question of what Ahab is, while somewhat obvious, is interesting and also ambiguous.  I already mentioned in response to Alison's post, that Ahab is a man/nature hybrid with his ivory leg.  Ahab in the bible was the King of Israel, i.e. King of the Jews.  In MD, he is clearly something of an anti-Christ, and there are quite a few references along these lines.  In Ch. 28 we get "...forboding shivers ran over me.  Reality outran apprehension; Captain Ahab stood upon his quarter-deck." And one sentence later: "He looked like a man cut away from the stake, when the fire has overrunningly wasted all the limbs without consuming them..."
Ahab spends much of this section of the book below.  In Ch 29: " 'It feels like going down to one's tomb,' - he would mutter to himself - ' for an old captain like me to be descending this narrow scuttle, to go to my grave-dug berth'". 

I don't think it's as simple as Ahab being the devil.  But in the order vs. chaos theme of Caitlin or man vs. nature theme of Alison (aren't these really similar, order=man, chaos=nature?)  Ahab is struggling to be human while battling his darker, chaotic nature that is literally attached to him at the hip.