Ummm, the definition of fiat can easily be looked up through wikipedia or any other definition site. Simply speaking, he's right and you're wrong. The accusation of BC being fiat is simply a streak of dishonesty of people who like to alter definitions in order to make their point. Any logic class teaches you the folly of using words that are ambiguous and can have multiple meanings. That's why for logic to work the definitions need to be strict and unambiguous.