Literature - William Blake - The Marriage of Heaven and Hell
I have loved 'The Marriage of Heaven and Hell' since I discovered it at age 16. It is fairly difficult to interpret, and part of it comes down to the influence of the visionary, Emmanuel Swedenborg, who influenced Blake so much.
As far as the 'voice of the devil', it seems that Blake is criticising the idea of perfection as a goal within Christianity, especially in the form of asceticism. There are some parallels between Blake's approach to this with Carl Jung in 'Answer to Job'. Jung points to the way in which Christianity tends to suggest the need to suppress and repress sexual desires.
Blake's philosophy is extremely interesting one in the way it came at a time when most people believed in the metaphysical reality of God and the devil. It is a contrast to the approach of Milton, even though Blake suggests that Milton was 'part of the devil's party without knowing it.' When I first read the passage it did trouble me because I was a practicing Catholic at the time and I thought that I was probably part of the 'devil's party because I was better at expression of the demonic side too.
It is important to note that Blake sees a duality of the soul and the body. Of course, it is rare to use the concept of the soul, and are more likely to use the term mind or self. I find the idea of 'Energy is eternal delight' inspirational and many others have done so too. Blake was an artist and poet who was radical for his time. He was also rather eccentric and a visionary. If he were alive today he would have probably been Sectioned for treatment in a psychiatric hospital and, quite likely, he would not have written and created the work for which he is known and loved by so many.