Question: What caused the Big Bang? Answer: Oneself.

What caused the big bang or cosmological inflation? We, the Singularity. We are the Singularity. There is only One Self (Oneself). Self Is. Sure we can make statements such as 'all is the mind' or 'there is only God' for indeed; so it is. God is (one) Self without a second. The perception of otherness serves the purpose not to be alone. It is not good to be alone. Genesis 1:1. Indeed: I:I.
~ Wald