>Here at my job we have a database modeler in our group. He is insistent that all tables use 'Natural Keys' and not surrogate keys.

Politics can be hard.

Perhaps an appeal to authority may help?

Here is the SQL guru Joe Celko discussing the issue - with references back to Codd:

http://www.informationweek.com/software/information-management/celko-on-sql-natural-artificial-and-surrogate-keys-explained/d/d-id/1059246?

We all know this, but here is the kernel of the argument - the article says it better than I can:
"If users can get to the surrogate key, they will screw up the data integrity "