[Probably wasn't worded the way he wanted it to be, but basically he means them both having too much of a dominate presence would disrupt their natural balance. A science driven world needs magic to take place in the form of "miracles" while magic can't necessarily be formed without at least some scientific or mathematical basics. Anything other than that would make it dog eat dog in a way... or something.]
Re: voice
Really...? Do you know why?