I have to disprove a negative so that you can accept a positive?You haven't shown there *is* a first cause: to do that, you have to first show there isn't an infinite regress of causes and *then* show that any two events have a common cause. Neither has been shown and both are unlikely.
What is interesting, is that here you are denying causality needs a first cause, at the same time as you deny Creation needs a God.
Do you think there might be a link there?
But then, you are so busy suppressing the obvious, I doubt you will even accept that this is the letter A: