II. Blood is a Very Special Fluid

This is all quite correct, but what about the remark that the devil is an enemy of blood and for that reason demands the signature written in blood? Can you imagine anyone wishing to possess the very thing he abhors? The only reasonable interpretation of the passage is that Goethe, as well as earlier writers of Faust legends, wishes to show that the devil regards blood as especially valuable, and that to him it is important that the deed is signed in blood rather than in neutral ink. The supposition must be that the representative of the powers of evil believes, or rather is convinced, that he will gain a special power over Faust by possessing at least a drop of his blood. It is quite obvious that Faust must sign in blood, not because the devil is his enemy, but because he wants to have power over him. The reason behind this passage is a strange premonition that if someone gains power over an individual's blood, one gains power over the person. In short, the feeling is that blood is a very special fluid and it is the real issue in the fight for an individual's soul between good and evil.