Perception

In this world, things are as you perceive them, or, at least, as some of you perceive them. The world can change with the right perspective, and a little bit of concentration; block off the trunk of tree with a finger, focus (hard, a nose-bleed might be in order), and when you remove your finger it will be as if that piece of trunk never existed. Of course, that tree is now floating ten feet off the ground, and if you turn away it's going to fall, good luck not killing anyone; you really shouldn't have picked a tree in the center of town...