I am indebted to Milton O Percival's William Blake's Circle of Destiny for the understanding I have of this subject. Quotations are from his book. This book is rarely for sale at a modest price but is available in many libraries. To find a library near you from which it is available try worldcat.com. If your local library doesn't have the book, you can ask them to obtain it on interlibrary loan.
Blake sees the status of man in terms of levels of existence. At each level man is capable of living according to certain principles which represent his level of consciousness. In ascending order the worlds through man may progress are Ulro, Generation, Beulah and Eden. Each level is characterized by the ability of man to perceive at that level, and the structure which results from that level of perception.
So we have in Ulro the ability to perceive at only the level of single or literal vision. Meaning beyond the superficial material level escapes single vision. Looking for information about the relationship between William and Catherine Blake in the prophetic books is confining oneself to Ulro thought, since it is looking for outward sensory data about outward sensory events. The most striking facet of perception in Ulro is the inability to see spiritual significance in anything that comes to us. Perception is turned outward only; the inner world is thought to be non-existent. Seeing only an outward existence creates the world of matter, rigid and passive.
Page 87: "This void in the empty East is Ulro, the Hell of Blake's myth. In this void the selfish emotions are activated by rational doubts and fears. ..Everything in this world is 'without internal light.' The souls which inhabit it have 'neither lineament nor form.'"
Ulro is the bottom of man's fall from eternity. If the fall had continued man would have fallen into the abyss of non-entity. The limits of Adam and Satan were set to prevent that from happening. When the limits were defined, man could start the rebuilding and return.
The agent for the the process of rising or returning is Los who gives form or concrete expression to the abstractions of Urizen in Ulro. In this way error is revealed for what it is and can be repudiated. This is our world where ideas and emotions are expressed in behaviors and personalities.
This is man's condition in the generative world: he is confined to the world of time and space, he is vegetated in a body whose limitations he cannot escape, he is receiving his information from shrunken senses. But there is more going on in generation; it is the world of transition from the outward and corporeal to the inward and spiritual. Los in the role of the holy Spirit is the agent of transformation.
Los's job is breaking down and building up. Breaking down by revealing error for what it is. Building up by creating Golgonooza in which man may exercise imagination. Spiritual vision becomes possible through the development of symbolic thinking. The object seen outwardly and corporeally becomes capable of carrying meaning which is inward and spiritual. 'The world of generation might indeed be thought of as a training school in vision.' (Page 272)
Page 273: "When the struggle is over, and the world and all that is therein can be seen, calm and assuredly, as the manifestation of spirit - then the soul has arrived at threefold vision and soft Beulah's light."
'To Be Continued' in my next post.