The 1978 classic Halloween revolutionized horror and spawned a series of sequels that are still running today. Yet after all these years, there still is no true consensus as to what exactly makes the killer, Michael Myers, tick. In Halloween: The Curse of Michael Myers, it was revealed that he was imbued with the "Curse of Thorn," an ancient druid curse... yet whether this should be considered canon is still up for debate.
The deliberate ambiguity that John Carpenter put into the character of Michael Myers has spawned numerous Halloween fan theories. Why is Michael apparently immortal? Why doesn't he speak? Why does he feel a compulsive need to murder people on Halloween night? These theories about the Halloween movies attempt to answer these questions and more. Some of them are frighteningly plausible, while others border on hilarious, but all of them are definitely worth pondering.
Michael Myers Is A Force Of Nature
It could be that nothing about Halloween was meant to be taken literally. Thus, the film is an allegory for whatever force of nature is behind every random murder that we see on the evening news. You cannot "kill" this force like you can kill a psycho killer: it will simply manifest somewhere else in another form.
Certainly, the film, through Dr. Loomis, goes to great lengths to suggest that psychopathology is not a sufficient explanation for Michael's condition. John Carpenter himself has repeated this point. Michael is rather "purely and simply evil." Dr. Loomis' conclusion is not meant to be taken as an indication that Loomis is a quack, but rather that psychiatry as a science cannot adequately explain that which is Michael Myers.
Michael's mask is meant, therefore, to represent a subversion of the "Mask of Sanity." Clearly, no one would mistake adult Michael for sane. Instead of an insane person wearing a mask of sanity, Michael is evil itself wearing a mask of insanity. In the film said evil is portrayed as a force of nature, "immovable like a mountain. It stands, where man passes away," as Samuels puts it.
Michael Myers Has A Congenital Insensitivity To Pain
A real condition, CIP is basically the inability to feel pain. Taking stab wounds, bullets, and third-degree burns in stride, Michael doesn't seem to let pain hold him back. The absence of any pain indicator would also explain his complete lack of empathy for his victims. He also uses this condition to his advantage in his workout routine, putting in extra reps to get the strength of 10 gorillas. (Why they are letting him use the Smith's Grove Sanitarium weight set at this point is another question.)
Dr. Loomis Is Actually The Same Loomis From Psycho
In this theory, the name Sam Loomis is more than just an homage to the iconic horror film and a subtle reference to Jamie Lee Curtis's pedigree. Think about it: what would a bereft Sam Loomis do after failing to save his girlfriend in Psycho? Maybe he decides to combat psychosis by going back to school to become a psychiatrist. He then decides to start fresh in Illinois, where he is assigned to treat a young boy who murdered his sister.
This theory actually makes so much sense that the only real reason to doubt it is that John Carpenter hasn't yet confirmed it as truth. It explains why Loomis isn't like a normal psychiatrist. He feels a personal duty to try and stop Michael as if this is a second chance for him. When Michael escapes and starts murdering, it would only make sense that Loomis would go on a crusade to stop him with the same obsession as Ahab seeking his white whale.
Michael's Purpose Is To Spread Fear
More than that, he either is, or is possessed by, a sluagh sidhe, an ancient Celtic spirit which emerged on Samhain. With Halloween being a Christianized version of the ancient Celtic holiday, it makes sense that such a spirit would be involved... but it goes much deeper than that.
Michael, imbued with supernatural powers, exists to scare people. His initial murder of his sister scared the town so badly that the house sat vacant for 15 years. Then, when people stopped being afraid (as demonstrated by Laurie's fearlessly walking up to the house and depositing the key), it was time for Michael to return. His purpose wasn't just to kill Laurie, but to create fear anew, which is why he built his own version of a haunted house at the Wallaces' place.
Furthermore, Dr. Loomis was complicit in the task of spreading fear, being controlled by the same sluagh sidhe as Michael, albeit unbeknownst to him. I mean really, an unhinged psychiatrist showing up in a quiet suburban town yelling about how the very definition of evil just showed up is a pretty good way to spread fear. Loomis succeeds in scaring the sheriff at least, who defers to Loomis during the investigation.