We can use our understanding of matter and energy and logic to describe it. Logically the only thing that can be eternal is something that is unchanging. From our understanding of matter and energy, matter and energy are not unchanging. So logically matter and energy cannot be an eternal source of creating universes. Which means that whatever the eternal unchanging source is it can't be energy or matter. Hence the only "thing" it could be would be something which is incorporeal which is in reality no "thing". Spirit is no thing. God is spirit.The flaw in your thinking is you believe you can actually know what that first cause was