DUKE Why, what an intricate impeach is this! I think you all have drunk of Circe's cup. (5.1.270)
The Duke, who is supposed to be the arbiter of law and order, and able to make sense out of confusion, declares that this situation is all madness. He alludes to the sorceress Circe of The Odyssey who transforms all the men to pigs by making them drink from her cup. "Their [the pig men’s] minds were unchanged, but their body’s, voices and heads were all swinish" (The Odyssey, Book X). All who drink Circe’s potion think everyone else is crazy, but that they themselves are perfectly sane. That does sound like the situation afoot in Ephesus. Even the law can’t sort this one out. It seems all is lost.
DUKE One of these men is genius to the other; And so of these. Which is the natural man, And which the spirit? Who deciphers them? (5.1.333)
Once again, law and order fail to save the day. The Duke, who should be the most sensible man in the city, decides that the root of the problem resides in the supernatural. He has no explanation to order the strange and sudden appearance of two sets of twins, and so he defaults into the same explanation of the supernatural everyone else used for the whole play. The Duke decides one man is "genius to the other," meaning something of an attendant spirit that was identical to a person, and believed to follow that person around though their life. No other explanation seems to fit their notion of order in Ephesus.