Four arguments against the existence of God

[Neo-Scholastic]

Summa Theologica, First Part, Question 2, Article 3 demonstrates the necessity of an unmoved mover, as part of the "1st way."

Do you mean: 1. Our senses prove that some things are in motion. 2. Things move when potential motion becomes actual motion. 3. Only an actual motion can convert a potential motion into an actual motion. 4. Nothing can be at once in both actuality and potentiality in the same respect (i.e., if both actual and potential, it is actual in one respect and potential in another). 5. Therefore nothing can move itself. 6. Therefore each thing in motion is moved by something else. 7. The sequence of motion cannot extend ad infinitum. 8. Therefore it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God.
Isn't this just the first cause argument with word 'motion' being substituted for 'cause'? Seems to me that it has the same flaws as every first cause argument. Why can't something be in motion on its own?

Firstly, this is not a stand-alone argument. The philosophy of how sensible objects preserve their existence while at the same time having the capacity for change traces back to Parmenides and up through the Scholastics. It is a modern mistake to assume that somehow a previous philosophy is refuted and replaced with the next. The fact is that each philosopher in the ancient tradition. Aristotle does not really undermine Platonism; but rather modifies and completes it, just as Aquinas builds on the foundation set by Aristotle.
The substitution of ‘[efficient] cause’ for ‘motion’ is another modern mistake. ‘Motion’ refers specifically to change. The modern conception does not include the formal, material, and final causes which are necessary for an intelligible theory of change.

It also assumes, without justification, that there can only be one unmoved thing. Other than to fit the presupposed definition of his god, what is his justification?

Parmenides’ argument about being changing can only apply to reality in its fullness, which is the All or One. There cannot be another All because then there would be two alls which is a contradiction. Is this the Christian god? Yes. In the Revelation to John it says that God is All in all.

He also seems to be guilty of affirming the consequent. In other words, he is saying that there are 2 sets: one that contains moved things, and one that contains unmoved things…To be meaningful, a set can't be empty, but more importantly, it has to have more than one object, or it is nothing more than a synonym for whatever is being argued for.

Again referring back to the tradition of which the argument is a part, the original question concerns how something can persist in its being while still being capable of change. For example, an oak goes from acorn to sapling to full grown tree, yet remains the same tree throughout all the changes. Thus there must be some aspects of the tree that change, because we do indeed observe the changes, and there must be something that does not change, otherwise you could not call it the same tree from moment to moment.

…the processes which allow for subjective experience are only understood in terms of physical relations between external stimuli that are transmitted and interpreted by the brain. Furthermore, you haven't even attempted to define non-physical…

Guilty as charged. I should have been using the term immaterial.

The abstraction is the ability to respond to external stimuli and through memorization separate it as well as change it through the formulation of intelligible definitions.

You have given a reasonable explanation of how people form thoughts by interacting with sensible bodies. You have not given is an account of to what aspect of the sensible body the thought refers. What I mean is this: at some point raw sensation gets turned into perceptions, presumably via physical processes in the brain. What quality of the external stimuli allows this process to occur? I say there is some immaterial form already there even if it is not alienable from material.