I have been studying Thomas Aquinas' philosophy for some time. Even though I've read a lot about the argument from motion pro and cons, I still haven't found an explanation for an obvious objection: why is it necessary to have a _chain_ of movers? Why cannot it be a circle, or a complete graph?

Every physical change is an interaction: the Sun moves the Earth, and the Earth moves the Sun (even though just a little bit). When you put an ice cube into a bottle of water, the water melts the ice cube and the ice cube cools down the water. Every object in the universe is in constant interaction with every other object – so why should we have a first one? How can we even identify which one is the mover and which one is moved?

Or, to put it into a concrete example: let's say that our universe contains only two objects: the Sun and the Earth (or a proton and the electron). The Earth is actually at position A, and potentially in position B. How would you identify the chain of movers when this potentiality is actualized? (the Earth is moved from A to B while moving the Sun to point C) What potentiality does God actualize here?

On Berkeley's view, illusions and errors of perception must be God lying, a very problematic position.

"The empirical by definition deals with the material." No. See Berkeley.

Yes the unmoving changer of the field changes and causes happening things to change and happen in the field . And caused there for the field its self to happen as a first place for action.There for the prime mover is the action inside the action. So action of its self does not move but causes the movement inside the action. Action is the unmoving part of the field. The field is then the continuum of the unmoving action.

I didn't mean that it was actualized but that it actualized something other.
I understand that pure act does not change, cannot logically change, but am trying to explain it rather than just asserting it.
I appreciate your help.

When the unactualized actualizer first actualized

It did not "first actualize." It is unactualized. That's like what made existence itself exist or what illuminates light?

Thanks. My specific concern is how to support that pure act cannot change. When the unactualized actualizer first actualized how did He not change at least by expending some energy?

It might. If it is a moved mover then it is also a mixture of potency and act, and therefore can be actualized. Pure act, because it contains no potencies cannot be changed.

YOS, does an actualizer change when it acts? Does pure act change because it acts upon potentials?
In your explanation of the solar photons does the sun change by acting?
I've read through a lot of this older thread but am not quite clear on this point. I'm trying to support the position that pure act is unchangeable.
Thanks.