MH is credited in comments I see with inventing the question "Why is there something rather than nothing." I have not read much Leibniz, but it is my understanding that is where the question in that form first appeared. I also saw someone credit the question to Heraclitus. It seems the pope liked the question enough to use it in a recent statement (as I recall, during his UK visit).

MH's answer is that all things are without a "why." I doubt the blogger can handle that, but it's about as theoretical as one can get.