Complex sentence: But the possibility that the "Dark powers" are not all "dark" and must obey certain rules of equality or equilibrium might be one possibility; has it not been said before that light and darkness cannot exist without the other ?
Split into simpler sentences: But the possibility that the Dark Powers are not all "dark" and must obey certain rules of equality or equilibrium might be one possibility. Has it not been said before that light and darkness cannot exist without the other?