Medium-the intervening substance through which impressions are conveyed to the senses.
Here is the situation: You have a body and a mind. The body state is experienced through the senses touch, hearing, etc. The mind is experienced as thought which creates a bank of memories that corresponds to experiences through the senses. The sum of these thought/experiences is Human Consciousness which is common and accessible to all like a cloud of information.
Depending on conditions, this cloud can become accessible in its entirety for various reasons like trauma, physical injury, an intense desire to tap in, or seemingly without cause. Often, a spiritual seeker that has had an awakening that reveals the awareness in spite of body and mind (witness), gets a glimpse of this and either lets it go and continues on, or they can take a vested interest (a calling) and strengthen, learn, and devote themselves along this particular line; developing their “psychic” sense to tap into the universal cloud of human consciousness. They become a medium to this cloud and for others who wish to draw information out of it but do not have the refined ability. (Note: Everyone taps into this cloud daily just by thinking of the past, or contemplating the future, the accessibility is just limited).
The thoughts in human consciousness that are congruent and match with the listener’s body (senses) are conveyed and pulled down from the cloud by the medium. Hence, making it personal to the individual. How does this apply to enlightenment?
Enlightenment is to experience and merge with the ground from which all things spring; revealing your identity as simultaneously being all things, times and places without a second of differentiation. What holds us from experiencing this ground is the identification with exclusive experiences, ideals, and concepts, to the exclusion of others. As well as sensations in the body as pleasure, pain, anger, excitement, etc. This forms the me that strives for “this” but marginalizes “that.”
So one must free themselves to the attachments they have in exclusive thought and sensation (mind and body) in order to touch their source.
A medium can help show a seeker where they still hold attachments in this cloud and its effects on the body. This works because often the seeker at this phase is still seeking enlightenment, happiness, whatever they call it, by establishing and strengthening or getting rid of certain mind/body conditions. Often, personality related attachments can be untangled with the help of a medium, releasing the seeker of heavy ties to this cloud of innumerable diversities.
Ultimately, to touch the ground from which all things spring which includes the sum of human consciousness, the sum of the egos, all sensations, everything inner and outer; one must like a laser beam turn inward. Which means ending the desire to seek experiences through the senses or the cloud of human consciousness. Then all energy is pulled to the center where the the Final Cause resides undifferentiated.