caloriesdont

It's only arbitrary if there aren't good reasons.

Dozens of reasons have been given in philosophy, it's up to you to decide if any of them work.

One of the big differences would be to point out that the universe is completely composite, whereas a foundation could be purely simple.

Josh Rasmussen is a great communicator about this!

Diving further into this, there's a hot debate about whether the universe does require a sustaining cause (the Existential Expiration thesis), or whether it can just exist unless something stops it from existing (Existential Inertia Thesis)

Personally, I am inclined to think that things tend to keep existing unless something stops them from existing, and that the universe therefore needs no sustaining cause.