I suggest directing some of your curiosity towards Google. This topic has been discussed many times before. In short: Your notion of "cause and effect" is not necessarily meaningful or applicable to all aspects of nature. Time could have been created in the Big Bang.

Also, it's possible that the entire process was continuous... the closer you rewind towards the big bang, the longer it takes to rewind just a little bit further.

http://www.fortunecity.com/emachines/e11/86/big-bang.html

Thanks for the link, it's interesting read. Even if time is created with Big Bang, and there are probabilistic quantum processes that don't demonstrate "cause and effect" in traditional sense these explanations come down to some singularity and suggest to accept that singularities just happen.

My personal favourite explanation is that since in the beginning there was nothing, there wasn't just no matter there were no rules. So there was no rule to say 'you can't get something from nothing' so out of true nothingness things would happen. And from there it was a matter of generating the right set of rules (which could have taken an unimaginably large number of iterations) where nothing was contradictory and then viola, the universe was ready.

This may be a meaningless question. If the very moments of creation of the universe are indeed the moments of creation of spacetime, what does "before" mean? Moreover, if the universe is "existence," how could we begin to perceive, imagine, or study existence without existence?

>how could we begin to perceive, imagine, or study existence without existence?

Through the deduction and reasoning. We don't exactly perceive sub-atomic and many galactic processes, but just infer their existence from some or other observation. Presumably "existence" is not entirely detached from "outside".

Yes but if the universe is everything that we perceive as physical, that is the material world, how could we possibly seek to examine the nonphysical world through the physical?

Consider, even reason itself is based on the rules and inherent properties of our physical universe. How can you examine a system which may not even have "reason"? Hell, our "physically" limited brains may not fundamentally be capable of comprehending such a system.

In essence, you may as well try to describe the nature of the supersensible using the sensible. It just doesn't make sense.

Our brains comprehended a lot of stuff which appeared to be incomprehensible. Relativity theory, quantum mechanics, most branches of mathematics are so abstract that have no direct connection to the real-world "physical" experiences of our brains and bodies. And yet some members of humanity (although quite limited subset) develop these areas and reason within them. If "reason" in the widest sense is such a fundamental law that it extends beyond the whatever singularity took place, then it might still be possible to deduct something. (Simplistic example) Imagine creatures living in 2D world that itself is in 3D world and sometimes interacts with 3D object. Should these creatures be able to deduct some information about "outer" 3D world after prolonged study of projections that sometimes suddenly appear in their 2D world?