@ficino,

I agree with Jeremy.

"As to the use Aquinas makes of Aristotle - I don't see reason to go along with his [or an earlier translator's] conversion of Aristotle's aorist verbals into present tense, because we don't know that a generator continually makes (present tense) light things light and heavy things heavy. He's not entitled to beg that premise; it needs to be established independently."

I think you are missing the point that Jeremy and I are making.  It doesn't matter if Aristotle did not spell things out precisely in the way that Aquinas did.  Aquinas was not trying to interpret Aristotle, but to describe the logical conclusion.  Existing material objects do not move themselves.  Therefore the Prime Mover must ultimately be responsible for the movement whether the movement is violent or natural, whether there are intermediate instrumental causes or the immediate cause of the Prime Mover sustaining the object's nature. 


From the Summa Theologica 1.8.1

[i]"  I answer that, God is in all things; not, indeed, as part of their essence, nor as an accident, but as an agent is present to that upon which it works. For an agent must be joined to that wherein it acts immediately and touch it by its power; hence it is proved in Phys. vii that the thing moved and the mover must be joined together. Now since God is very being by His own essence, created being must be His proper effect; as to ignite is the proper effect of fire. Now God causes this effect in things not only when they first begin to be, but as long as they are preserved in being; as light is caused in the air by the sun as long as the air remains illuminated. Therefore as long as a thing has being, God must be present to it, according to its mode of being. But being is innermost in each thing and most fundamentally inherent in all things since it is formal in respect of everything found in a thing, as was shown above (Question [7], Article [1]). Hence it must be that God is in

@ficino,

Here is a link to the Summa Contra Gentiles:

This is the presentation of the First Way from the SCG.

"[3] Of these ways the first is as follows. Everything that is moved is moved by another. That some things are in motion—for example, the sun—is evident from sense. Therefore, it is moved by something else that moves it. This mover is itself either moved or not moved. If it is not, we have reached our conclusion—namely, that we must posit some unmoved mover. This we call God. If it is moved, it is moved by another mover. We must, consequently, either proceed to infinity, or we must arrive at some unmoved mover. Now, it is not possible to proceed to infinity. Hence, we must posit some prime unmoved mover."

There are a total of 35 paragraphs where Aquinas goes through the objections and reasons.

But in particular you've indicated that you don't know why Feser considers a sustaining cause pertinent.

He seems always to wind up arguing that contingent things need a necessary being to keep them from popping out of existence.

Material things move either naturally or violently. Material things that are in natural motion move as a result of their form/matter combination.  So whatever sustains them in their particular form/matter combination is the ultimate cause of their motion.

[i]"[8] In the second way, Aristotle proves the proposition by induction [Physics VIII, 4]. Whatever is moved by accident is not moved by itself, since it is moved upon the motion of another. So, too, as is evident, what is moved by violence is not moved by itself. Nor are those beings moved by themselves that are moved by their nature as being moved from within; such is the case with animals, which evidently are moved by the soul. Nor, again, is this true of those beings, such as heavy and light bodies, which are moved through nature.[u][b] For such beings are moved by the generating cause and the caus

@Strawdusty,

Ha Ha.

My GPS reads the same whether I get sunburned or not.  There are different senses of a thing *changing while remaining the same*.

@RomanJoe,

"However he does bring up a good point. When something is in uniform motion it moves from point A to B to C (theoretically ad infinitum)."

But things cannot move ad infinitum in a finite universe.  See Aquinas's commentary on Physics Book 6 around 881.
Uniform rectilinear motion cannot be infinite.