Do go to see the newly acquired etchings by William Blake at Tate Britain, or take a look online (http://www.tate.org.uk/learning/worksinfocus/blake/ ). They display all the unsettling power and apocalypticism we expect from this exceptional, romantic artist.
One shows a young man tethered to a globe of blood by his hair. In another, someone burns in a furnace. Underneath, Blake has written lines such as, "I sought pleasure and found pain unutterable," or, "The floods overwhelmed me."
What you won't find in the gallery, though, is any explanation of these visions. Instead, Blake is treated as impenetrable, his imagery obscure, his calling idiosyncratic. He's rendered slightly mad, and so safe. We can look and admire, but like a modern gothic cartoon strip – that his art no doubt influences – he can be enjoyed, but not taken too seriously.
That's a shame. For not only can Blake be read. What he says carries at least as much force today as it did two hundred years ago.
Consider one of the figures who is in the new works: Urizen. He's well known as he's the same figure who appears as Blake's famous "Ancient of Days" – an old man, with Michelangelo muscles, a full head of long white hair, and a wizard-like beard. Urizen is a key figure in Blake's mythology.
He is not God. (Blake thought it laughable to imagine the divine as a father-figure, as God is found within and throughout life, he believed, hence referring to Jesus as "the Imagination.") Instead, Urizen is the demiurge, a "self-deluded and anxious" forger of pre-existent matter, as Kathleen Raine explains. His predominant concern with material things is signified by his heavy musculature. He is variously depicted as wielding great compasses, absorbed by diagrams, lurking in caves, and drowning in water – as in the new Tate image. It shows that his materialism has trapped him.
Blake loathed the deistic, natural religion associated with Newton and Bacon. He called it "soul-shuddering." Materialism he dismissed as "the philosophy in vogue." He thought the Enlightenment had created a false deity for itself, one imagined by Rousseau and Voltaire as projected human reason. The "dark Satanic mills" of Jerusalem are the mills that "grind out material reality", as Peter Ackroyd writes in his biography of Blake, continuing: "These are the mills that entrance the scientist and the empirical philosopher who, on looking through the microscope or telescope, see fixed mechanism everywhere."
Urizen is theirs. The demiurge presides over a world that suffers under the tyranny of the laws of nature, and Urizen is as imprisoned by the constraints of space and time as are the individuals who follow him. "He who sees the Ratio only sees himself only," Blake mused. The materialist's view of the world is a prison because it's a world created by limited perceptions.
So far, so predictable, you might think. The man who saw visions on Peckham Rye (Peckham Rye!) is bound to be an idealist, even a spiritualist. (Though he once remarked that the unimaginative see ghosts; the truly inspired, he continued – tapping his head – see visions.) But he speaks more broadly.
For one thing, there's an important political dimension to Blake, because the liberty he sought was of both body and mind. He was a fierce republican, on occasion getting into trouble for damning the king. He read Mary Wollstonecraft and boasted of knowing Tom Paine, though he must have disagreed with them too, on account of Wollstonecraft's rationalism and Paine's deism. He was sure that spiritual freedom must be worked out in the world. He interpreted the political troubles of his day as reflections of an inner, spiritual turmoil, and although he didn't gain a substantial audience in his own times, he was quite clear that his vocation was as a public prophet. He wanted his work to be seen.
There's another crucial aspect, too. Blake did not merely demonise his opponents, but recognised himself in their philosophy as well. The Ancient of Days is a figure he returns to repeatedly. Urizen is a subject that produces some of his finest work. Raine explains that he is exploring his own psyche in the bearded old man who is "enslaved by his own ego." If Jesus is called "the Imagination", Satan is called "the Selfhood" – an association that is more psychological than theological. It's the inner part of me, and you, with which we must fight for freedom, he is saying. That's why, underneath another of the new works at Tate Britain, he writes: "Everything is an attempt to be human."
His illustrations map the spiritual drama he envisaged every person undergoing. Their "truth" is revealed in so far as they engage you – and that they do so by unsettling, by disturbing. Blake offers us symbolic figures that are half familiar, as if we've seen them before, in forgotten dreams.
© Mark Vernon is a writer and philosopher. An agnostic with a keen interest in religion and spirituality, his books include The Meaning of Friendship , After Atheism  and Teach Yourself Humanism . An honorary research fellow at Birkbeck College, London, his own venture is called The School of Life . Mark's website is entitled Philosophy and Life , and has been listed among the Sunday Times' best blogs.
This article is adapted from one on Guardian Comment-is-Free, with thanks and acknowledgment.
Also on Ekklesia: 'William Blake liberates the Bible for the people', by Christopher Rowland. http://www.ekklesia.co.uk/node/6386