What do you think the universe is? Do you think it existed by itself? Anything that begins to exist must have a cause.
The question right now is whether the universe is contingent on the cause or is it self-sufficient and- Self-existing?
We believe that God did not begin to exist. We believe God is self-sufficient, eternal, immortal, all-knowing, all-powerful. These are the attributes of God, what defines Him as God.
The necessary being is never dependent whereas the contingent being is always dependent.
If something that doesn’t even exist, how can it bring about something that does exist like the universe?
The only alternative is something. It cannot be nothing.