Thank you for trying to explain, and perhaps I can use your analogy of the bucket to better illustrate the original question.
The Creator is He to which everyone gives the name God. He’s the First Cause as explained in Aquinas’ Second Way. He creates the bucket. Now obviously the bucket can’t be moved from potency to actuality until after it’s been created. Only after the bucket has been created by the First Cause, can the Unmoved Mover change it by means of moving it from potency to actuality.
So Aquinas is describing two distinct acts. In your analogy they would be the act of creating the bucket, and the act of filling the bucket. One act performed by the First Cause, the other by the Unmoved Mover. Aquinas refers to each of them as God, and so we’re to assume that they’re simply separate attributes of one God. But how does Aquinas justify this identification of both the First Cause and the Unmoved Mover as God, and specifically as one and the same God?
Answer:
I covered this point in Post 82 by stating that all of the five arguments (motion, order, necessity, grades of beings and origin) are based on the Cosmological argument, that all things have a cause, all of the five arguments have as their foundation the argument from cause and effect . That is, if you trace things from effect to cause, we will come to the first cause which can not explain itself, it can not cause itself, necessitating an Uncaused cause. If we regress infinitely from effect to cause,infinity is this case means indefinite regress we will have no beginning, or there can be no indefinite regress in causes. If there is no first uncaused cause there can be no second caused cause The truth that everything has a cause is proven from empirical knowledge found in the examples of “for every action there is a reaction” or If I drop something, gravity will cause it to fall, If I don’t eat I will die etc, etc. So all things have a cause, caused by the Uncaused Cause, creation, motion, necessity, being, and order. These five arguments are a small amount of the total amount of arguments, these are regarded as the classical ones that St.Thomas used