Not all deities are omnipotent.
As I will shortly demonstrate, there is only one unmoved mover, and it is omnipotent.
Perhaps you mean that not all historical conceptions of deities entail omnipotency. This is because those conceptions are false.
Why? Maybe you should try justifying a claim every once and a while.
My apologies; I assumed (obviously incorrectly) that you were already familiar with the argument, given that you were arguing that it is wrong.
The unmoved mover argument is concerned with why things change (motion, in classical times, carried with it the connotation of any change, not merely a change in position). Suppose I am pushing a rock along the ground with a stick held in my hand.
Obviously, the rock is not moving itself. It is being moved by the stick. And obviously, the stick is not moving itself, either -- it is being moved by my arm. My arm is moving it because motor neurons in my arm are firing. Those neurons are firing because electrical signals from the nervous system instruct it to. My nervous system emits those signals because my frontal cortex instructs it to. And so on, up and up through elementary layers of reality -- through laws of gravitation and conduction, the weak and strong force, that govern the mechanical operations of the brain.
In each case, the movement (change) in one thing is initiated by something outside itself. Again, the rock is moved by the stick, the stick by my arm, my arm by motor neurons, motor neurons by electrical signals, etc. This is not an ordering
per accidens, the way a father has a son who in turn has a son. Rather it is an ordering
per se, in which each movement of an object occurs solely because it was compelled to by another movement somewhere up the causal chain.
Obviously, nothing can cause itself to change. A rock would not spontaneously start moving; it would move because it was pushed, or because gravity pulled it down a slope, or some similar effect. And also obviously, no such chain can be without a beginning (although it need not necessarily have an end): it must be started at some point. Hence, an unmoved mover. Because it must be the first thing in this causal chain, it cannot have potential to be anything else -- it must be pure being, or pure actuality (if not, then it would need to have ITS potential to actualize other things actualized by something else and therefore it would not be the start of the causal chain).
Now (and here we veer into the First Cause argument), it is also the case that a thing cannot actualize something's potential except by endowing it with some feature of itself. For instance, a lighter can only actualize a thing's potential to burn or melt or become warm; it cannot actualize its potential to become cold. Likewise, water can actualize, say, a sugar pill's potential to dissolve; it cannot cause it to turn into something else entirely, like an apple.
If this is the case, then anything which actualizes a thing's potential must have derived its ability to actualize from something higher up the chain, which in turn derived that ability from something higher up the chain. Since we've already established that this chain ends (begins, rather) in an Unmoved Mover, it follows logically that that being has the power to do anything which is capable of being done, because it is from that mover that
all actualizing power in the universe ultimately derives. Hence, omnipotence (of which omniscience is a component).
And there is said to be only one First Cause/Unmoved Mover because to establish a distinction between two things is to imply deficiency in one and supremacy in the other. For instance, if John is taller than Jim, than Jim is deficient in height; he has unrealized potentiality in terms of his height. To have a deficiency is to have unrealized potentiality, and the Unmoved Mover, being purely actuality, has no potentiality at all.
Bear in mind, this is merely an argument for the existence of a (single, omnipotent) God. It is not, as you have noted, necessarily an argument for the Christian conception of God -- but then not even Aquinas himself asserted as much. It is, however, the basis on which natural law theory (and thus Christianity as a whole) is built.
But once you have established that there is an all-powerful God, the rest is all questions of technical details, anyway.
Obviously you would benefit from a better reading by a more talented writer, which is why I recommended Feser's book.
Really? Are you arguing an eye twitch can't happen without divine intervention? This is laughable.
I am arguing that it is impossible for a thing to cause itself to happen, since for it to do so it would have to exist in that state already.
I am also arguing that it is impossible to have a causal chain that has no beginning (though it is distinctly possible for it to have no end).
What this means is that the Unmoved Mover argument is not, as Dawkins and other atheists fraudulently (or ignorantly) misrepresent it, an argument for a temporal first cause -- that God created the universe at some distant point in the past. It is an argument that
God is sustaining the universe in every moment, and that without his active effort to do so, the universe would cease to exist.
