Insights on the movie (SPOILERS)

Some commentators absurdly suggest that Thomasin is better off at the end than living within the religious confines of her family or the Puritan community. Really? She now gets to slaughter babies in the woods and eventually face eternal damnation; yeah, that's just so incredibly liberating. Would she really be happy joining a bunch of murderous beasts, a couple of which just slaughtered her family? Interestingly, grinding babies to death is presumably female emancipation in this "folktale" and that's not too far from reality in modern Western culture.

Other commentators suggest that we don't know if what's going on is real or the result of mental illness due to extreme religiosity or a perhaps even a nightmare. ANSWER: Yes, we do know. From almost the very beginning we KNOW there's an actual diabolical witch in the area, which we SEE stole the baby and bathes in his blood. Shortly later we observe that this satanic ritual brings back her youth (or, at least, the appearance of youth); and she seduces Caleb, showing that she's a friggin' pedophile. The only thing we don't know is if there is more than one witch or what the devil's place in the events is or isn't, both of which are revealed literally in the final act.

Furthermore, if the witch is a delusion of one or more of the family members then that means that Thomasin or one of the others took the baby; of perhaps an animal. So where's the body or remains and why weren't William & Caleb able to find it during their thorough searches? If one of them or an animal, like a wolf, took and killed the infant where's the evidence, where's the blood? We see zero evidence to draw this conclusion.

Also keep in mind that the movie is subtitled a 'folktale' and is based on actual documents from the 17th century. In other words, the movie doesn't depict reality, but is exactly what it says it is -- a folk TALE where ugly, evil witches who bathe in infants' blood and devils who masquerade as goats really lurk in the dark woods and are to be feared.

So the surmounting tragedies the family experiences aren't a product of hyper-religious paranoia or a nightmare, but rather the result of confrontation with sinister beings, both physical and spiritual, which exist in the 'world' of the movie.

Lastly, the message of the film is obvious: Don't leave the strength and protection of the community of believers due to arrogance or you'll be picked off one by one by the Enemy; or, at least, seduced into joining the dark side.