On the surface, it would seem that it is not unreasonable to claim that Blake was a believer in Christianity. For one thing, my understanding is that he himself professed to be a Christian. Moreover, his poetry was greatly influenced by the Bible and at least one of his most famous poems, "The Lamb," appears to reflect Christian orthodoxy in its language: "Little lamb who made thee?/Dost thou know who made thee?/Little lamb, I'll tell thee,/Little lamb, I'll tell thee:/He is called by thy name,/For he calls Himself a lamb./He is meek, and He is mild;/He became a little child." This is obvious a reference to the Lord Jesus Christ as "the lamb of God." Furthermore, Blake expressed his contempt for religious skeptics like Voltaire and Rousseau in his poem "The Scoffers": "Mock on, mock on, Voltaire, Rousseau,/Mock on, mock on; 'tis all in vain;/You throw the sand against the wind/And the wind blows it back again." Then there is Blake's behavior on his deathbed. According to the artist George Richmond, a friend of Blake:
He died ... in a most glorious manner. He said He was going to that Country he had all His life wished to see & expressed Himself Happy, hoping for Salvation through Jesus Christ – Just before he died His Countenance became fair. His eyes Brighten'd and he burst out Singing of the things he saw in Heaven. (as cited in Wikipedia)
The sentiments and behavior of Blake in his final moments would certainly seem appropriate for a devoted Christian. Nevertheless, I would argue that we must consider other evidence--evidence that would suggest that Blake was, in fact, not an orthodox Christian.
First of all, as anyone who is at least somewhat familiar with Blake's poetry would know, Blake had a very antagonistic attitude toward the institutional church. He was often scathing of organized Christianity. In one of his poems, a child says that church is “cold” and compares it unfavorably with a tavern! In his poem, “I Saw a Chapel All of Gold,” he speaks of a serpent in a chapel “vomiting his poison out/On the Bread and on the Wine./So I turned into a sty,/And laid me down among the swine.” Some might argue that Blake’s attitude was not a reflection of heterodoxy, but rather of his frustration with the hypocrisy and cold formalism of the institutional church in his day. After all, this was also the time of John Wesley, who also rejected the spiritual deadness of the established church in England.
However, Blake was not merely critical of the church as an institution. The fact is that he espoused a number of views that were in direct conflict with orthodox Christian belief. For example, he once said of Jesus: “"He is the only God ... and so am I, and so are you." (as cited in Wikipedia). In other words, every person is divine—an idea that contradicts the Christian belief that God is altogether separate from mankind and which conflicts with the central Christian doctrine that Jesus is the unique Son of God. He apparently faulted Christianity for its supposed suppression of human sensual desires, in contrast to the many Biblical warnings about succumbing to the lures of the flesh. He denied the virginity of Mary at the time of Jesus’ conception. Furthermore, Blake appears to have been influenced by the ideas of the Church of the New Jerusalem, founded by followers of the supposed prophet Emanuel Swedenborg, who, among other things, claimed to have conversed with beings from other planets and held that the Second Coming of Jesus had already occurred. Blake’s religious beliefs may have reflected gnosticism—the idea that salvation is not through faith but through esoteric knowledge. And yet, as almost anyone who has knowledge about the early history of Christianity will know, gnosticism was firmly rejected by the Church. Finally, consider that in his poem “Epilogue,” he addresses “my Satan” and says of him: “Tho’ thou art worshipped by the names divine/Of Jesus and Jehovah…” In other words, he seemed to equate Satan with Jesus (God the Son) and Jehovah (God the Father), or, at least, was suggesting that those who were worshipped Jesus and Jehovah were really worshipping Satan—either clearly blasphemous notions for a Christian.
In short, it seems that if Blake was a “Christian,” he was a very odd one, since he rejected nearly all of Christian doctrine. In fact, it could be argued that Blake’s self-identification as a Christian reflects the fact that he had developed his own idiosyncratic version of “Christianity.” In this, he was not unlike many other figures over the centuries who proclaimed that existing Christianity was hopelessly corrupt and wrong and needed to be replaced with something better—Joseph Smith, the founder of Mormonism, comes to mind as an example. However, to be fair, perhaps it is possible that Blake had a conversion to orthodox Christianity before his death and that is reflected in his deathbed behavior. Perhaps he did, or perhaps he was just horribly deluded as to the truth. Of course, no human being can know for sure which of these scenarios is correct…