We will assume for the sake of argument that we live in an eternal Universe that changes.
It is in the nature of our Eternal Universe to change.
1) Change is the realization of potency.
2) The realization of potency cannot regress infinitely because if it did there would not be in existence an actuality that wasn’t itself a realization of potency.
3) This involves a contradiction because potency cannot actualize itself from nothing and yet the sum of all change is reducible only to potency since every act in the chain is itself a realization of potency. Therefore change should not exist.
4) But change does exist. Thus there must be an actuality that is not itself a realization of potency and instead is that which causes and sustains in existence the realization of potency from all eternity.
5) Because this act is not itself a realization of potency we can say that this act is not itself changing and is instead pure-actuality.
Conclusion) This pure-actuality cannot be identical with the universe since it is in the nature of the universe to change.
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