Q. How do you know its spirit talking to you and not imagination.
Good question! Let me say first of all that mediumship could not work without your imagination.This is where spirit are able to put images words etc. The less imagination you have the harder to get through to you.
with practice you will also learn to experience the difference between the energies of Psychic and spirit. It is a knowing, a sensing, with practice you will get to know the difference. when a fully fledged medium is working they should be able to give exact evidence. Things no -one else knows about. Even if the recipient has to go and ask family etc. to check out the information. when it is proved right what better evidence could there be. No one could pick yhat from ones mind!