On the Origin of Dreams and Visions

I found a work called Spiritual Experiences which is a diary of sorts by Emanuel Swedenborg, concerning his supernatural experiences. Here are a couple of quotes concerning the origin of dreams and visions.

CONCERNING VISIONS OF ANCIENT TIMES, AND THE PRESENT

"True dreams are described in a different way. Here, a dream means the kind of visions that take place at a time of wakefulness, when the mind is withdrawn from outer sensations and passion. At such a time, the mind, left alone to itself, sees everything displayed to it as if before the eyes. Such dreams as these are elsewhere called visions, and they occur in full daytime, when a person is wide awake. One really sees mentally the symbolic displays themselves, not as thought sees, but as external sight does, outside of itself. It is clear that such visions existed in the earliest Church, especially with these patriarchs, and indeed, in full wakefulness. They are portrayals of the Messiah Himself and the things that must come to pass. I can affirm that such displays do occur, even in the daytime, and in fact, so vividly that one may see the spirits themselves and many things that take place in heaven. This has often happened to me, and at the same time, angels spoke with me. This was also the case in the earliest Church among the patriarchs. Heaven and earth were joined together so closely that those who were in the heavens spoke with those on earth, and the reverse, and thus portrayed symbolically those things which would come to pass. This is how revelations took place at that time."

ON THE ORIGIN OF PROPHETIC DREAMS

The following quote I found interesting, for it reveals the origins of prophetic dreams (I hear of them constantly):

"As for dreams in particular, I would like to say this, that they are brought upon a person by spirits. Dreams by which future events, as well as truths, are revealed, are brought on by spirits of God the Messiah, but the rest by spirits who are not of God the Messiah. But dreams by which people are deceived are caused by evil spirits, thus by the devil's gang. Furthermore, dreams are brought on either by means of actual voices, or for the most part by displays in their countless forms. One who is not acquainted with these can never learn the meaning of symbolic dreams. For the portrayals of realities in heaven are effected by means of the same sort of things as there are on earth, especially those which are gazed upon, thus objects of nature. Sometimes they are composed in such a way that they can hardly be unraveled unless one is acquainted with the individual types of displays. That dreams are of this nature appears very clearly from the dreams of Joseph, as well as of the Pharaoh, and notably those in the books of the prophets, where much is read about dreams. This is not to mention actual visions when people are awake. These visions are also altogether like dreams, being the same kind of displays, just like real life, as if in clear daylight, also at times of wakefulness before and after sleep, as well as other times. There are likewise actual portrayals, when the spirits are presented in person just as one person would be to another on earth; but this happened to me when I was in a different state. With some, the dreams brought on by spirits are only illusions amounting to almost nothing but games."