Spirit fascinates me. The most fascinating fascination is that Things That Are True are true whether you believe in them or not. God exists and doesn't need for you to believe that "he" exists. What you call this energy and how much you "believe" in it does not affect It, it affects you.
What many in the spiritual community are referring to when they say "your truth" is actually "your perception," which is, to you, true.
Every Medium works differently and will get different information because every Medium is human and has a different perception which governs their perspective of existence. We are telling you the truth from our perspective.
If you and I are standing face to face, and I say this oak tree is on my right, would you argue with me because clearly, the oak tree is on your left? No, because we understand how the world works and that my perception is influencing my description of the tree. We don't even process it consciously because it is an accepted concept.
HOWEVER - very few of us (myself included) understand how the Universe, how Existence works, specifically the spirit realm. So much of our communication about it is from our perception of it. That is the only way we can communicate something that is beyond our human senses.
If you are lost in the wild, how do you know where you are? Triangulation. You use three different points to orient yourself. I don't mean that you should go to three different Mediums to verify information, nor that you shouldn't trust what we tell you. BUT - know that if you don't understand or recognize the information, your reading is just one of the waypoints. Another waypoint may be your intuition or knowledge, and another could be your experience. Put the information in its proper role.
Probably everyone on earth has had a dream they can't describe, or an experience, or a feeling that defies language. Does this mean it didn't happen? Of course not. Communicating what we perceive is often limited by language and the other person's understanding.
What is proof of Truth? Experience. When a Medium gives you a piece of information that you feel is true, it doesn't matter if it's perfectly communicated, because you are becoming part of the experience. Most Mediums want you to be able to connect to spirit by yourself and should offer some teaching in how to do this, what to look for, where to learn more. It is the experience of connection that shows you Truth. Yes, it is truth from your perspective - at first.
Over time, these experiences translate into Universal Truths - that the soul is eternal, that Source is Love. It's not enough for someone, even your loved ones through a Medium, to tell you that you are loved and are eternal - you go through Perception to Truth when you experience it - which is where you started, isn't it?