"Why is there anything rather than nothing?" Accept the question as a koan, not a challenge to debate, and you will have a mystical experience, although you may need to walk away from your screen, still your mind, and sit alone quietly in your room for a few minutes before the strange wonder that the question points to begins to register.
The "answer" to the question is not a proposition. It's an experience — of astonishment, as you stop in your tracks before the inscrutable reality that things . . . exist, your own self being the thing you feel most keenly. You didn't will yourself into existence. How did you get here? Look to your parents, and from there to their parents, and so on, back to . . . primordial dust? The Big Bang? Bracket for a moment the question of what we should call the thing where that regression into the past comes to its final stop. Bracket the question of what the thing is exactly. That it was there, rather than not there — that's the stubborn mystery.