Because, you see, the great man himself, Carl Gustav Jung, that sick bastard, he figured it out, you see? He figured it all out. He learned from Freud and took it to new dimensions, which were really old dimensions, but Jung didn't know about that at the time, but ANYWAY...
So yeah. Synchronicity. Acausal events that are related - not related in any direct fashion as we know it, but superseding something...some kind of metaplane where all of this made sense to someone, you know, the kind of shit we like to call "coincidences" but just line up a LITTLE TOO WEIRD for anyone's comfort. Like, when you're thinking of calling someone, and you pick up the phone to dial their number, and there's no tone because the friend you were gonna call decided to call you AT EXACTLY THE SAME TIME and you both pick up at the same time and you're VERY disconcerted - see, that right there is a synchronicity.
But that's exactly the kind of thing you can't predict, you can't explain.
Now, quantum mechanics, which is responsible for a great many things (like, um, computers), states that you can never know everything about a particle, because if you shoot an electron of light in order to illuminate it, that affects the particle, and the results change. Therefore, there are nothing but really good guesses. This really kicks science in the pants, because there's no Aristotlean/Newtonian precise mathematical formula to rely on anymore, there's a table of possible results and observations, ranked in order of likelihood/occurence.
And there's no more straightforward cause and effect, because EVERYTHING is related, and everything affects something else, and picking a flower in Connecticut might cause the Japanese economy to crash.
So tread carefully, y'hear?