TITLE: What do coherent topoi have to do with completeness?
QUESTION [6 upvotes]: There is a theorem of Deligne that a "coherent" topos (e.g. one on a site where all objects are quasi-compact and quasi-separated) has enough points (i.e. isomorphisms can be detected via geometric morphisms to the topos of sets). I've heard it said that this is a form of Goedel's completeness theorem for first-order logic.
Why is that? 
I'm sorry for not providing more motivation, but I don't know enough about this connection to  do so!
This is now posted on MO as well.

REPLY [2 votes]: There is now an accepted answer on MO.
(I'm CWing and accepting this to make it clear that this question was answered.)