At the end of the movie, we learn that John Doe has killed Mills' wife and unborn daughter, and goads Mills into killing him, thereby becoming Wrath. Two problems:
Mills wasn't particularly wrathful before he killed John Doe. So if it weren't for Doe, he never would have committed the sin in the first place. Isn't that sort of unfair? He punished Mills before he'd even done anything wrong.
He was wrathful before, not to the point of murder, but he was angry and impulsive throughout. One establishing moment was when John Doe shows up at a crime scene disguised as a photographer, and Mills basically threatens to beat the hell out of him.
This may be when John chose Mills as his Wrath victim. In the ending scene Doe tells Mills how disturbingly easy it was for a man of the press to purchase information from the men in his precinct. This implies Doe went to the police station specifically to purchase information about Mills.
Since Doe actually committed two sins, wouldn't he technically have to die twice to be fully absolved? Or was absolution not his aim? If it wasn't, what was?
I seriously doubt absolution was Doe's concern. In his mind, he felt as though he was chosen by God to make an example out of humanity and himself as well and whether or not he went to Hell because of it was not up to him. If that's the case, chances are he probably didn't care if he himself had two sins to atone for instead of just the one.
Plus, John Doe is just insane. He wants to kill one person for each sin, but, uh oh, I don't have anyone for Wrath. No problem, I'll just manufacture one, God would totally want that.
"It's more comfortable for you to label me 'insane.'"
But what if Doe wanted himself to be the Wrath victim, seeing how he, you know, is a serial killer?
But if so where is Envy?
John Doe envied what Mills had (e.g. wife, "children", a "normal" life)
The deadly sin of Sloth generally means being a lazy bastard who couldn't get off his ass to save his life. Yet, the chosen victim for that sin was apparently a drug dealer and child rapist. Wouldn't that make him more guilty of Wrath, or possibly Greed?
Drug dealers might not be "lazy" so to speak, but they contribute to a lifestyle that encourages Sloth for everyone else. Also, as Topher Grace stated in Traffic, "You can go out on the street and make five-hundred dollars in two hours, come back and do whatever you want to do with the rest of your day." Given how fast money can be made through their "trade", drug dealers, especially very well connected middle-men, generally let their clients seek them out. We never got any indication that the victim was particularly wrathful or any greedier than any of the other drug dealers in the city, pederasty notwithstanding, but Doe more than likely chose him because of his connection to the Greed victim (a city attorney who got him absolved of said pederasty in court).
Also, Sloth is not just laziness. Sloth is the sin of moral complacency and indifference. But yes, the drug-dealing pederast seems like an odd choice for that sin.
Not when you consider that drugs are often used to create complacency and indifference. People get addicted to things like heroin to give themselves a high that counters the low of their lives and the lives around them. It's a selfish addiction that changes nothing, and just urges people to forget and ignore instead of being active in change.
A drug-dealer would also often be indifferent to the health and well-being of his clients, selling drugs that either destroy the body or relationships. As long as he gets paid, he wouldn't care what he inflicts on others.
The last two deaths don't fit in with the pattern of the others. In the first five, they were killed by an overabundance of their sins (although Greed is a little shaky in that regard.) If we count Mills' wife to be the sixth death, then she didn't die because she was envious. She died because someone was envious for her. That would be like saying that the victim of Gluttony would be someone getting eaten to death. The same goes for John Doe. If he is the victim of Wrath, he didn't die because he was wrathful, he died because he made someone else mad. This is solved somewhat if you consider John Doe the sixth death, and Mills the seventh death (assuming he dies from the death penalty), but it's still a leap.
The last two sins are Envy and Wrath, they don't have to be deaths, as seen with Sloth, so they are Doe and Mills respectively.
The wife isn't killed for any sin, just a victim of Doe's envy, just to make sure no one is hanging on to the idea that Doe is virtuous in his killings.
Also, Mills would probably not get the death penalty. While he did murder an unarmed, handcuffed suspect, the dude was a serial killer who had just killed Mills' wife - and her unborn child, which Mills didn't know about until Doe told him - and shipped her dismembered head to him in a box. Under the circumstances, "extreme emotional disturbance" would be open-and-shut here, which means decades in a prison and/or mental institution, but not death. Unless, of course, Doe had meant to "kill" Mills' spirit, but maybe not his actual body. Then he succeeded without question.
The novelization establishes that Mills won't get the death penalty, and he'll likely not get the maximum jail time possible for killing Doe because of the circumstances, but he'll definitely serve time.
Also, those would not be the only two killings that don't fit the supposed pattern: for Lust, Doe forces a john to kill a prostitute by raping her with some sort of strap-on dagger-dildo. It's presumably not the prostitute who was committing the sin of Lust, however, but the john. So it's really a pattern of four, out of seven, in which Doe kills the sinner in a manner appropriate to the sin, and three in which Doe engineers the killing of someone else, i.e., the prostitute, Tracy Mills, and himself, as a victim of the sin in question. So really, there are two patterns.
It's been stated the victim of Lust is the prostitute, although shouldn't the victim of Pride be more accurately considered as victim of vanity?
The two final victims are John Doe (Envy) and David Mills (Wrath). It's all built on the penal system in use during Dante's lifetime. A man sentenced to death could either be executed or his wife and children could be. The loss of his entire family was considered equal to taking his life. That is exactly what Doe does to the Wrath victim, only he kind of lucked out on the part about the child. This is all foreshadowed earlier when he says to Mills "what life I will allow you to have".
From above points, considering Sloth isn't dead yet, isn't his work still kinda incomplete?
So sensitive if you shine a flashlight into the man's eyes he'll go into shock? For all intents and purposes he is dead.
While the Gluttony victim was certainly guilty of his sin, he did not, to our knowledge, actually harm anyone or commit any crimes. By most modern definitions, that would mean he is innocent. So why do Mills and Somerset appear to agree with the serial killer about his lack of innocence?
It didn't seem so much that they were agreeing with him on any of his points in that speech, more stunned by his venomous rant.
Would being tied to a bed for a year really destroy your mind to the point where you bite off your own tongue? Don't get me wrong, it would take quite a while to get over something like that, but I think you would have to be tied up for at least a decade to get to the state seen in the film.
Bedsores can develop extremely quickly, within a couple of days. Imagine the pain that he would have been in after being in the same position for a whole year. He's also wasting away, only fed enough to be barely kept alive, is getting no sunlight at all and it's not as if he'd be able to get up to go to the toilet so he's likely lying in his own waste as well. I'd think slowly rotting on a bed for a year being unable to move would definitely mess up your mental state. In addition to this, the only person he sees for a year is an insane madman. At that point, he's biting off his own tongue in an effort to commit suicide.
When John Doe turns himself in, the police explain that he's been cutting the skin off his fingertips for quite some time, hence why they couldn't find any fingerprints in his apartment. But just after the police find the Sloth victim, the killer shows up to take Mills's picture and his fingers seem to be perfectly unharmed, nor does he appear to be wearing gloves. Just a simple continuity error, or am I missing something?
Throughout the film it becomes clear that the pattern is Sin. The detectives understandably take the simpler view that these are a pattern of murders based on the Sins, where really the pattern is the Sins themselves. This is exacerbated by Gluttony being the murder of a man via force-feeding and Greed that of a biblical 'pound of flesh' punishment (there was actually a small chance the Greed victim could have survived). These first two make it look like Doe's motivation is solely based on murder. The Sloth victim is the first misstep in the perceived pattern as he is not dead - the motivation was demonstrating the sin. The Lust victim is not actually guilty of Lust (though Doe still feels contempt for her being a 'disease-spreading whore'), the client is. Again the motivation is the demonstration of the sin rather than truly punishing the sinner. Doe does admit that he enjoyed 'turning each sin against the sinner', but as mentioned already, you don't have to kill the sinner to turn their sin against them. The Pride victim is another demonstration, where Doe is attempting to show society that some people are so full of Pride (in this case the sin is the very modern syndrome of obsession with one's physical appearance) that if they are deprived of the focus of their Pride they would rather end their own life. In the Pride case, Doe specifically disfigures but very carefully bandages the victim, ensuring she would not die unless by her own hand. The last two are very subtle demonstrations and fit in with Doe's belief that his 'work' will be pored over and studied endlessly. Doe believes himself to be guilty of Envy (specifically of Mills' life and his wife) and so turns this sin against himself by killing Tracy and thus destroying the object of his envy, with the greater purpose of tipping Mills over the edge into giving in to his Wrath. When Mills kills Doe, his sin of Wrath (which Doe had already noted was a trait of his when he commented that Mills would likely assault or even kill him if left alone with him in a windowless room without fear of consequences) is turned against him, completing the list of Sins.
So, in a way. Doe tried to purify his victims AND himself, trying to save them from their sins. This fits in with his belief of him doing God's work.