There is a new book out by journalist and former philosophy grad student Jim Holt called Why Does the World Exist? It’s worth reading if you’re interested in questions like that.
Nowadays, when people ask why the world exists they are generally asking why the Big Bang occurred. Unfortunately, nobody knows. The most common answers are that either some random quantum event or some higher being made it happen. Some physicists think that our universe is just a small part of reality and that the existence of a vast, possibly infinite, collection of other universes explains why ours is here and/or why ours is the way it is.
As soon as a particular cause or reason for our universe to exist is suggested, however, it is natural to ask why that cause or reason is the explanation, rather than some other cause or reason. Why are the laws of quantum mechanics in effect? Where did God come from? Where did all those other universes come from?
This is why the answer provided by a Buddhist monk at the very end of the Why Does the World Exist? is my personal favorite: “As a Buddhist, … he believes that the universe had no beginning….The Buddhist doctrine of a beginning-less universe makes the most metaphysical sense….A billion causes could not make the universe come into existence out of what does not exist”.
Perhaps the reality that exists beyond our universe or that preceded the Big Bang (the super-universe, the multiverse, the quantum foam, whatever it might be) always existed and always will. It simply was. Or is. It never came into existence, so no cause, reason or explanation is necessary or even possible. Perhaps it’s cyclical. Perhaps it’s not. Perhaps it’s always changing. Perhaps it isn’t. But it had no beginning and might have no end.
The great 17th century philosopher Spinoza referred to all of existence as “God, or Nature” (Deus, sive Natura): “That eternal and infinite being we call God, or Nature”. I prefer “Nature” to “God”. To Spinoza, it was the same thing and it was eternal.