"Mediumship without a faith context is a parlor trick.
I've come to believe something: The most important single thing any human being can ever know is that life is Eternal. You will always be. Forever. This is something Christians all profess as a matter of dogma. People "believe in" the afterlife, but few know, know that life is Eternal.
You'd think knowing God is real is most important, but I'd disagree. God can be real and Time can be a cosmic side-effect with life just a biological accident. I think if Jesus came to make anything clear, to prove something for all of us to know it is this fact: we are Eternal beings. He took care to show us that not just when He appeared to His disciples as the Resurrected Christ, but during the Incarnation in the event we call the Transfiguration:
Truly I say to you, there are some standing here who will not taste death until they see the kingdom of God.”
About eight days after he said this, he took Peter, John, and James and went up the mountain to pray. While he was praying his face changed in appearance and his clothing became dazzling white. And behold, two men were conversing with him, Moses and Elijah, who appeared in glory and spoke of his exodus that he was going to accomplish in Jerusalem.
Peter and his companions had been overcome by sleep, but becoming fully awake, they saw his glory and the two men standing with him. As they were about to part from him, Peter said to Jesus, “Master, it is good that we are here; let us make three tents, one for you, one for Moses, and one for Elijah.” But he did not know what he was saying.
While he was still speaking, a cloud came and cast a shadow over them, and they became frightened when they entered the cloud. Then from the cloud came a voice that said, “This is my chosen Son; listen to him.”
After the voice had spoken, Jesus was found alone. They fell silent and did not at that time tell anyone what they had seen.
Most Scripture interpreters focus on Moses and Elijah representing the Law and the Prophets here, and the scene justifying Jesus as the Son of God to the Jews. I don't doubt this was part of God's plan. But we something else here: we see Jesus visiting with two people who have passed and receiving information from them. We see, in a word: mediumship.
Keeping in mind that the Old Testament condemns the practice of "conjuring the dead" what we see is Jesus, self-declared Lord of the Sabbath, showing us how in prayer by Grace those who are alive and well on the Other Side can communicate with us. God approves this scene in front of the witnesses.
We so we learn a lot of things here; one of them being that it cannot be a sin to do what Jesus does. We also learn the way things are supposed to work, that we here (Church Militant) and they over there (Church Triumphant) are a partnership of living souls meant to be of service to one another in love of God. This is clearly spelled out by Pope Paul VI in Chapter 2 of Indulgentiarum Doctrina.
You are a Medium
If you are a person of faith you already know how this works, you just perhaps don't think of it this way. Most people have had the experience of praying about a problem and suddenly having a clear idea of what to do accompanied by a sense of peace. Someone gave you both the answer (information) and peace (validation that it's the correct course). Alternatively, you might have found the answer by asking a friend, Pastor, or just seeing something on TV. Still, that sense of peace accompanies receiving the information.
Let's go back to Jesus. Why didn't God just give Him the information about His "exodus?" If you believe Matthew and Mark's versions of the story, He did. Jesus referred to being handed over before He went up the mountain. He went off alone to pray all through the Gospels, this time, He takes three venerable witnesses. What is Jesus showing them? Partly, He is showing them who someone is in the previous paragraph. Someone is the person on the Other Side who gives you the answer, leads you to the person who has it, or gets your attention during the TV show.
I said previously that we are not good. We are also, pretty much clueless. It all comes from God. The inspiration to serve the dying untouchables on the streets of Calcutta. The desire to give a few dollars to a charity. To listen politely and even act as if interested when that old lady in line at the store starts to talk. We have, to steal a word from the New Age: guides. And every person here is imbued with the ability to hear and respond to them. Some people seem to be able to hear from individuals and get such specific information that a even atheists are convinced: we never die. These are those we call "mediums." It's what I found I could do. I'm not sure everyone can't. I'll be telling my story here shortly.
I don't know much beyond that. I don't know if there is a one person or a group, if they are our own relations or just those God sends. I don't know if they change or stay the same. I don't care. Our job is to turn matter into spiritual energy through prayer and works of mercy that they can use to give us the information and help we need to bring the Grace of God into Time. We must know life is Eternal, that none of this material crap means anything. We must know that willingness to die to self is not giving up a single thing but gaining a huge spiritual presence in Time.
We hold the death of the Lord, deep in our hearts.
Living, now we remain, with Jesus the Christ.
We are the presence of God; this is our call.
Now to become bread and wine: food for the hungry, life for the weary,
for to live with the Lord, we must die with the Lord.