Presumably you're referring to Jean Bodin (he's the only person in the relevant period where Wikipedia mention inflation)? I don't recall Bodin arguing that currency must have some inflation, only that inflation - where it existed - had a cause (he pointed to bullion importation from the New World as the cause in his time). My memory is hazy, though, and I do remember not really covering the pre-Classical economists much, because economics as a discipline didn't really get going until Adam Smith et al.