Are they of God, of the Devil, or could they be natural born abilities of Man?
I guess it all depends upon what we define as psychic abilities. Obviously someone who is in the business and takes on the identity of "A Psychic" is using enhanced abilities fueled by spirits that are not in league with God. But there is a big difference between being psychic and being A Psychic. Just like there is a difference between prophesying and being A Prophet.
There are also quite a number of psychic abilities, which are not necessarily all relate so perhaps the rules don't apply the same to all situations. But just for starters (especially for those who are unfamiliar and don't yet understand what I'm talking about), the major psychic abilities coincide with the 5 physical senses. Those who can see things in the spirit realm are called "clairvoyant." Those who hear things in the spirit realm are "clairaudient". Clairsentience is feeling, and there are others for smelling and tasting. "Clair" meaning "clear", and "voyant" meaning "vision", "audient" meaning "auditory"... I think it's origins are in the French language. There are dozens of others, namely precognizance and claircognizance (knowing the future and knowing facts for no explainable reason), but I think thats a pretty good foundation to get this discussion started.
Personally I think the major psychic abilities are similar to artistic abilities and are natural to Man. Not everybody has them in equal amounts. Artists can relate to musicians and poets, but each of the fine arts are their own thing, and either you have what it takes to make it in those fields or you don't. Same goes for the senses that allow us to perceive things in the spirit realm. On some level they are each an ability and a form of art, and most people that have them operate in more than one, but each is unique in it's own right.
What usually happens though is we are inspired by unseen forces whether we want to or not. Many artists look for their muse, which often times is a spirit that enhances their natural abilities and makes their work stand out. People with psychic abilities do the same. In Church we are taught to listen for the voice of God, so those who see, hear, feel, smell, sense the future, or just know stuff can be influenced accordingly by the Kingdom of Heaven. Those who want to use their abilities for the other side (often without realizing it), might tune their senses in to spirits of the dead, spirit guides, or pagan gods. Go to a church of Spiritualism and they will teach you how to become a medium, which essentially is being a prophet for the dead.
As a musician I have learned how to yield my talent to the HS and allow inspired worship to flow through me. As someone who's clairaudient I have learned how to tune into the voice of my God and be obedient to Him, and how to speak on His behalf to other people. But I have also learned how to hear quite a number of other spirits, some appear to be rather neutral and some are clearly not. But just like when I'm playing guitar, the talent is my own unless I am inspired by other forces.
I guess where I'm making the distinction is the difference between the ability to HEAR God, and yielding to Him. Many hear His call, but few answer. Or on the flip side, hearing spirits and yielding to them instead. For those with the natural born ability, the hearing part happens regardless. But just like everything else in life, we choose whether we submit our talents to God or not.
