Question

Hello Rabbi,
I saw on YouTube a discussion that took place between you and Zvi Yanai about evolution.
There you proceed from the assumption that this universe is not a necessary existence, and consequently, according to the principle of sufficient reason, we would have to arrive at a factor that is a necessary existence.
I wanted to ask why?

After all, I can posit a God that does not exist, just as I can posit that our world does not exist.
Why is this different from that?

B. Also, if anything, one could even assume that this world is a necessary existence based on our experience, since energy can never be lost, only converted and changed in form.