First, Schrodinger's Cat: Photon emitter, pointed at a half-silvered mirror, such that 50% of the wave hits a sensor that activates a gaseous poison emitter inside a box that has a cat in it. Standardly, we think about it this way: the photon hits the halfsilvered mirror and decoheres into a superposition of "straight" and "reflected", then the sensor decoheres into a superposition of "hit" or "not hit", then the poison emitter decoheres into a superposition of "activated" or "not activated", then the cat decoheres into a superposition of "dead" or "alive"... so the cat is both dead and alive, etc. Isn't it obvious that upon opening the box, the human decoheres into a superposition of "sees an alive cat" and "sees a dead cat"? Isn't that blindingly obvious? If the cat can decohere, why can't the human? And that's all Manyworlds is, is assuming that decoherence doesn't suddenly "stop" at macroscopic levels. Can someone explain to me why this isn't selfevident?