While i was out i thought of a way to weight the different voices:

George (essentialist): bad guy
Thessaly (essentialist): not a true bad guy, but not a sympathetic character at all
Wanda (non-essentialist): unreservedly one of the good guys, and a very sympathetic character

It's just that a lot of readers seem to think that George, in explaining that Thessaly, the moon, and the gods all hold the essentialist view, and the fact that the plot follows the essentialist course, is speaking with the authorial voice.