It's strange that psychic powers if they exist should be at all debatable. If they exist they should be obvious. Think of the incredible advantage such powers would give any creature in the battle for survival. Certainly this would be something that evolution would select for - heavily. So given even a tiny bit of psi existing, it would eventually be developed by evolution to be one of our main senses, if not the main one. It seems strange that the most aggressive testing of humans now reveals tiny psychic effects (according to believers) or none at all. If it exists it should be something that we use continually. Or here's another way of looking at it. We did develop incredible psychic powers through evolution: the ability to sense objects at a distance (sight and hearing), the ability to detect the proximity of objects (smell), etc. To a rock, if it could think, those would seem like amazing, magical abilities - psychic powers even. But these abilities were physically possible and so we developed them. We have not developed clairvoyance or other psychic abilities because they are not possible. So, in a way, we are as fully psychically developed as possible!