Yes, it's much like the placebo effect. I feel that the mind can have direct physical manipulation, but the real question is wether/how much one is able to effect others and how much one's reality is effected by/effects that of others. For example I feel that if one truely believed without a doubt that he could fly then it is so, but other people do not believe that humans can fly. As such, will they see him fly? If he jumps off a high building, will he die? etc.