As I've noted before, vampirism is a tricky plot device, and the modern tendency to extend cheap grace to all and sundry makes it worse. The usual way out is to have a creature that is merely vampiric without being an actual vampire(see the first link again). The "Twilight" series goes beyond that by trying to redeem vampires.
It doesn't work. The main theological problem is that vampirism involves drinking blood, which is always under a curse. Leviticus 17: 12–14 mentions this, and it’s echoed for Christians in Acts 15: 20, 29. The point is that the blood of a creature (human or not) represents its life, so drinking its blood means appropriating its life, which is how vampires work. It’s also a parody of the Atonement, because just as we live eternally by spiritually partaking of Christ’s blood and life, so the vampire prolongs its existence by partaking of a creature’s life. This is true even when the blood is taken from an animal: the idea of "good" vampires using rodents instead of people doesn't eliminate the problem.
Yet the unique idea of the "Twilight" series is that the change is effectively good, or anyway not evil. Instead of "Choose life" we have "Choose (un)death." Considering how confused zand outright persverse our culture is concerning abortion and euthanasia, such an attempt to make death a positive shouldn't come as a surprise.
And there is a point of theological interest in putting a spiritual or allegorical spin on vampirism. Early Christians were considered vampiric because they drank the blood of Christ in their rituals.
But that's the rub: Christian "vampires" would be a eucharistic crowd; they would subsist on the only blood freely given for that purpose. And while Christian theology stresses dying yet living, it won't fit well in the undeath category. We are not less alive than before; we are overflowing with the life of God Himself.
In fact, it would be nearer true to say that we are all vampires by birth, lacking life and trying to suck it from things around us that can never truly fill or cure the void. It is only in Christ that we find sufficient life to do the job, restoring us to true life from our twilight of undeath.
1 year ago