This is a big question and one that I shall not attempt to gain a definitive answer to in the space of this article.
We exist- so what caused us to exist?
There are some who might like to argue that we do not realy exist. I personally do not accept this view. If you did not exist, you would not be able to deny you exist.
However, what if WE exist, but the world around us does not and is just an illusion? This is the classic "Brain in a vat" idea, the notion that the world around us could simply be something akin to the type of world presented in the movie "the Matrix". Well, it's possible, i'll grant that.
The third option here of course is that we do indeed exist and that the world around us exists. We must then ask , what caused us? What caused the world around us to exist?
Nothing caused us to exist?
Is it possible that we have no cause? Well that would go against common sense and against the established scientific law of cause and effect. Did the universe and ourselves just pop out of nothing? I personally don't see this is as being a reasonable position to take. If you have ABSOLUTELY nothing, then there's never going to be "something" spontaneously arise from it. You can't get something from nothing. It's impossible.
So therefor it stands to reason that SOMETHING must have caused us to exist. But what?
Did the universe cause us to exist?
Perhaps the universe has always existed in some shape or form? Or there exists an infinite regress of universes? Maybe the universe itself has just spent such a long time evolving until eventually we get to the point we are at today?
Firstly, as far as I'm aware, there is simply no hard evidence that our universe was created by another one.
As for whether or not our universe itself was not created, but existed forever, I'm not sure.
There is a theory known as the "big crunch" theory, which suggests the universe is like a rubber band- expanding and contracting, and that when the universe contracts it results in a big bang (rather than a black hole), which started this present form of the universe, and is destined to go on having on exanding and contracting, one big bang after another, forever.
However, there doesn't appear to be any concrete evidence for this theory and recent scientific discoveries have observed that the universe is not being slowed down by gravity, but is instead speeding up.
Even so, for me this still doesn't explain how a universe that presumably is not itself a conscious being with personality and emotion can give rise to conscious beings with personality and emotions?
The universe is said to work according to certain "laws" and "principles" - the major choice is between whether the organising force behind these laws and principles is blind, impersonal, unconscious chance, or a conscious, personal creator.
I accept that the existance of God is a possibility. What I struggle with is the fact that we cannot see God. We cannot detect God with any of our senses or any of our scientific instruments.