Something interesting: I've read the other day that Bach when he wrote his WTC there he didn't know the terms *major" and "minor".
I can't find the source again but may be someone can help me. May be we'll find it in the comment of the Bach society or even in the faksimile.
I was wondering about this remark as I've also read that since Zarlino the modes have been reduced to this two kinds of tonics - even we know that Bach still was using church chorals in different modes.