The poems constituting Blake's Urizen cycle—The First Book of Urizen, The Book of Ahania and The Book of Los—present his most sustained nightmarish portrayal of the fallen world as seen from the perspective of a philosophy that strips the natural world of divinity. The philosophical first cause of the cataclysmic events in these poems is Urizen's Newtonian metaphysics; though he is here unnamed, the shrill trumpet blast, which had been blown by Newton to usher in the dark modern age in Europe, sounds again in the first chapter of Urizen. Blake's conflation of cosmology and embryology in the poem testifies to the fact that Newtonian philosophy had influenced the discoveries being made in the eighteenth-century life sciences. Ironically, however, emerging vital materialist physiologies, though voicing allegiance to the laws of Newton, ultimately described a living world that could not be explained by his metaphysical system—a state of affairs that I argue Blake dramatizes in the Urizen cycle. Despite their non-Newtonian aspects, the vitalist natural philosophies were for Blake another form of natural religion, for they too denied divinity to the self-active living matter of the universe. This chapter argues that Blake satirizes both Newtonian law and the materialist embryological theories that transgressed it, presenting equally horrific visions of a petrified world in which man is enslaved to a transcendent, abstract deity, and of a violently monstrous chaos teeming with repugnant forms, which, in contrast to The Marriage, are portrayed as unholy. On Blake's reading, either philosophical perspective, in positing an immaterial God separate from the universe, or in implying that the divine is altogether unnecessary, occludes the living, intelligent, energetic flames that comprise the infinite, divine universe.

But in the Urizen cycle, Blake's pantheist counter-vision is not delivered as forcefully as in his earlier works, or in The Song of Los's conclusion. This is partially due to the fact that unlike with No Natural Religion's “b” series and The Marriage's Devil, no protagonist or speaker articulates Blake's philosophical perspective.