Everything that can happen does

This idea came to me on a walk today, listening to a podcast about the Persian philosopher Avicenna (Philosophy Bites). Avicenna said that the universe is made up of contingent things, and so must itself be contingent, and caused by a necessary thing. Which means there is some necessary entity which caused the universe.

Well, maybe we have the wrong perspective on cause and effect. Maybe, rather than things causing other things to happen, things PREVENT other things from happening. This would lead to the same, deterministic outcomes we see in the world around us, so long as there ARE things to prevent forces interacting in any other way (which, according to the laws of physics, there are). But then when it comes to explaining why the universe is here, we can say, standing before matter came to exist "Is there any reason there shouldn't be matter?" And it seems the answer was "No", since matter did come to be. Hence there being something rather than nothing, without a need for a necessary cause like God.

I foresee several problems with this, which I don't quite understand enough to put into words in this tired state in which I'm writing. But one is that we still seem to need to explain why what exists, and only what exists, exists. If it wasn't specifically caused, why did it come to be as it was? Or is this just one of an infinite number of possible universes that came to exist?

...I'm sure I read once that quantum physics says that everything that can possibly happen DOES happen, by the world splitting off into two parallel universes. Which didn't bother me too much at the time, since I think there is only one thing that can happen- that which does- so that things would remain pretty much as they seem under that conception. But then quantum physics I think suggests otherwise there as well? I know there are theories of quantum uncertainty and infinite universes somewhere in quantum physics or string theory or something...

Eek. Why do I always have these outlandish thoughts before bed-time, and why don't I keep them to myself until morning? Meh. Anyway, if you're reading, please hurl some criticism at the basic thought for me, that perhaps everything that can happen does.

Much as grassy arse