Dreams are a kind of trance-like states. Dreams are not always caused by the person himself, but can also be imposed by the will and concentration of a higher spirit. This means that people sometimes have dreams that are given to them in spirit. The spirit imposing the dream, so to speak, may be doing this to protect someone or give a warning. These so-called clairvoyant dreams can only be received between the third and fourth degrees of sleep, the half-waking sleep stage. In the fourth degree of sleep, there is no more conscious dream experience, because then the organism is no longer able to receive the inspiration. Therefore, people who sleep very deep cannot receive spiritual or clairvoyant dreams. Thus, it is important for soul and body to be in harmony in order to receive such dreams. During awakening, one usually knows what has been dreamed, unless one is in the deep sleep phase.
Source: Quotations from the books of Jozef Rulof:
-A dream is like being in a trance. There are seven levels of trance conversions, of which the seventh equals apparent death. These attune- ments are unknown on earth, it’s impossible for man to detect them. We are the only ones who are able to do this because we have shed our physical body. To come back to your dream which you experi- enced yourself, in other words: it emerged from out of your inner condition, although it was imposed upon you by me. So you dreamt because I wanted you to, by means of my will and the concentration of my thoughts, which is a condition in itself. So a person can have dreams which have been given to him in the spirit. Your dream was a condition of feeling, imprinted on you by concentration and strong will power.
A View into the Hereafter p.229,230 (VI.12944.12951)
-Now the Other Side suddenly influences and the spiritual connection is achieved. This unity usually serves to protect these people from something, a warning, for example, which is achieved by a family member, the guardian angel of the earthly being.
That happens a great deal. You can even be reached in your sleep, but then you will have to dream what people want to give you. These are clairvoyant dreams and they can only be given to you. This clair- voyance wakens you up and can be received between the third and fourth grade of sleep. This is half-waking going to sleep. If you go to sleep normally, then you pass the threshold of the third grade into the fourth. However, there is nothing more to be dreamt here, because here the organism cannot receive this inspiration, because inspiration is influence and you are disengaged. Soul and body must therefore be in harmony with the dream received and this is, as I say, the half-waking conscious sleep. While wakening up you now know what you have dreamt. In the fourth grade of sleep there is no more experiencing, this has been disengaged by sleep. Anyone who therefore sleeps very deeply, which means the normal sleep for the fourth grade, cannot receive any spiritual dreams.
Spiritual Gifts p.326 (SP.8033.8044)