When we investigate the material world, as we refine our analysis, we eventually come down to :
Once you are there Leibniz's question was : "Why is there something rather than nothing ?"
Unless you bring into the picture a completely different kind of explanation, such as a creator, you can't really answer that question !
When you come to the most refined state of awareness - which is devoid of any particular content except for its own lucidity and clarity - if you ask again
"Why is there something rather than nothing ?", here too you have to say "It is simply there and I can only acknowledge it."
The same is true for all other behavioral manifestations (3G's, 5 skandha's, …). If we follow the flow of activity through the brain :