Innocence, it seems, is a nice way of saying ignorance, which would imply that the gaining of wisdom is a hard process, full of rude awakenings, startling revelations, melodramatic shifts in cosmology as one continually learns that the neat scenario one had while younger , with their neat and simple relationships predicated on convenient cause and effect, is grossly inadequate.
God gave us senses so we may learn from our experience and cobble together as we go along, a practical philosophy of everyday life. Wisdom, if you like. It seems that one is likely to realize that they are a victim whether they like it or not, and that the blissful sleep of ignorance of one's state of being exploited and abused is illusory at best. Norman Mailer had once said that he thought stupidity was a choice people make , and ignorance, likewise, often enough seems a willful defense mechanism that relieves one of their obligation to use their senses to grow and work within the world as an active, creative agent. This is the crucial issue for Blake, to believe in a God will intercede and make everything okay with a kiss and a feather or a promise of endless bounty on the other side of this life, or that one is here with the senses a Creator gave him or her, with a brain that can process and organize experience into a framework, narrative perhaps, the keeps the world that is both fluid and coherent.
The final belief is to believe in a fiction, which you know to be a fiction, there being nothing else. The exquisite truth is to know that it is a fiction and that you believe in it willingly. --Wallace Stevens
The belief in a fiction, I assume, is that one believes less in the fiction's generic outline of the relationships between personality and the delicate details of the atmosphere , and more that the fiction works as a means that enables individual and collective imaginations to commit themselves creatively to what other wise would raw, unknowable data. We are the author of our own book, so to speak, we are all writers of a particular fiction that enthralls us, and the key to a belief in an operative narrative form is to realize that we can change, alter and modify the fiction as needed. Not that it's an easy thing to toss off, as an after thought. But we make our narratives from the things we do , and this reminds me of the oft-quoted line from Vico, paraphrased here: Only that which man makes can man know.