If our universe did not always exist, however, but came to exist suddenly, there would have to be some sort of cause for this. While it is certainly possible for something to exist without a cause, nothing can BEGIN TO EXIST without a cause. Without some sort of cause, the beginning of the universe would never have happened and it would not currently exist. Some force would have to be behind the creation of the universe. It would have to be a supernatural force, since nature could not have existed prior to the creation of nature. It would have to be intelligent for it to have created all of the natural laws. It would also have to be timeless, since it created time while creating the universe. A supernatural, intelligent, timeless force. In other words, God.
Most scientists will agree that the 'Big Bang' has been essentially proven to have happened, though they frequently disagree as to whether it created matter and energy out of nothing, or merely transformed previously existing matter and energy. But think about this: Did the Big Bang create a relatively orderly universe like we have now? Or did it create a chaotic universe that gradually became orderly over time? Either one is in direct violation to natural laws. I'm not saying that natural laws cannot be violated, but they can only be violated by a higher power than nature. According to 'naturalist' theory, there is no power higher than nature. 'Naturalist' theory is obviously wrong, then. For nature to have begun to exist, or for nature to have always existed yet not fallen into entropy, requires some force more powerful than nature, a force that is able to control nature. In other words, God.
Of course, whether the 'God' as I've described is the God mentioned in the Judeo-Christian Bible is an argument that I've asked not to get into at this point. If one rejects the existence of God altogether, arguing the point would be moot. Only if one accepts (at least hypothetically) the existence of God could we really delve into that question. Let me just say that I believed in God for many years before I even started looking at the Bible, and most of those who reject the Bible do not reject God. I would even say the reason most people believe in God is not because they've contemplated the scientific evidence at hand, but because God created us to know Him. It was His purpose for putting us here in the first place, so it comes naturally to us.
Our primary obligation is to the truth. If God exists, it is wrong for someone to pretend that He does not. The only way to prove the existence of God to yourself is to be willing to believe, to open your heart to God, and 'let there be light' in your life.