After re-reading your posts, it seems that you are only focused on the First Way and that it lacks an exhaustive argument for a sustaining cause.  Is that correct?  Or is your argument that Aquinas gives no reason for proposing a sustaining cause at all?  

If your complaint is merely that the First Way does not argue exhaustively for a sustaining cause then I may agree that it is not exhaustive.  But as we have been discussing, natural motion that is occurring in the present moment is being caused by another, according to Aquinas with that "other" identified as the generator of the form, God.  God as the sustaining cause of the object is implied although at this particular point he does not elaborate.  It would be hard to imagine how he could argue for an Unmoved Mover if natural things essentially moved themselves and did not need an Unmoved Mover once they existed.

But he does provide reasons in other places and specifically addresses the question if things need to be kept in being by God here:

ST. First Part. Q104


I answer that, Both reason and faith bind us to say that creatures are kept in being by God. To make this clear, we must consider that a thing is preserved by another in two ways. First, indirectly, and accidentally; thus a person is said to preserve anything by removing the cause of its corruption, as a man may be said to preserve a child, whom he guards from falling into the fire. In this way God preserves some things, but not all, for there are some things of such a nature that nothing can corrupt them, so that it is not necessary to keep them from corruption. Secondly, a thing is said to preserve another 'per se' and directly, namely, when what is preserved depends on the preserver in such a way that it cannot exist without it. In this manner all creatures need to be preserved by God. For the being of every creature depends on God, so that not for a moment could it subsist, but would fall into nothingness were it not kept in being by the operation of the Divine power, as Gregory says (Moral. xvi).

   This is made clear as follows: Every effect depends on its cause, so far as it is its cause. But we must observe that an agent may be the cause of the "becoming" of its effect, but not directly of its "being." This may be seen both in artificial and in natural beings: for the builder causes the house in its "becoming," but he is not the direct cause of its "being." For it is clear that the "being" of the house is a result of its form, which consists in the putting together and arrangement of the materials, and results from the natural qualities of certain things. Thus a cook dresses the food by applying the natural activity of fire; thus a builder constructs a house, by making use of cement, stones, and wood which are able to be put together in a certain order and to preserve it. Therefore the "being" of a house depends on the nature of these materials, just as its "becoming" depends on the action of the builder. The same principle applies to natural things. For if an agent is not the cause of a form as such, neither will it be directly the cause of "being" which results from that form; but it will be the cause of the effect, in its "becoming" only.

   Now it is clear that of two things in the same species one cannot directly cause the other's form as such, since it would then be the cause of its own form, which is essentially the same as the form of the other; but it can be the cause of this form for as much as it is in matter---in other words, it may be the cause that "this matter" receives "this form." And this is to be the cause of "becoming," as when man begets man, and fire causes fire. Thus whenever a natural effect is such that it has an aptitude to receive from its active cause an impression specifically the same as in that active cause, then the "becoming" of the effect, but not its "being," depends on the agent.

   Sometimes, however, the effect has not this aptitude to receive the impression of its cause, in the same way as it exists in the agent: as may be seen clearly in all agents which do not produce an effect of the same species as themselves: thus the heavenly bodies cause the generation of inferior bodies which differ from them in species. Such an agent can be the cause of a form as such, and not merely as existing in this matter, consequently it is not merely the cause of "becoming" but also the cause of "being."

   Therefore as the becoming of a thing cannot continue when that action of the agent ceases which causes the "becoming" of the effect: so neither can the "being" of a thing continue after that action of the agent has ceased, which is the cause of the effect not only in "becoming" but also in "being." This is why hot water retains heat after the cessation of the fire's action; while, on the contrary, the air does not continue to be lit up, even for a moment, when the sun ceases to act upon it, because water is a matter susceptive of the fire's heat in the same way as it exists in the fire. Wherefore if it were to be reduced to the perfect form of fire, it would retain that form always; whereas if it has the form of fire imperfectly and inchoately, the heat will remain for a time only, by reason of the imperfect participation of the principle of heat. On the other hand, air is not of such a nature as to receive light in the same way as it exists in the sun, which is the principle of light. Therefore, since it has not root in the air, the light ceases with the action of the sun.

   Now every creature may be compared to God, as the air is to the sun which enlightens it. For as the sun possesses light by its nature, and as the air is enlightened by sharing the sun's nature; so God alone is Being in virtue of His own Essence, since His Essence is His existence; whereas every creature has being by participation, so that its essence is not its existence. Therefore, as Augustine says (Gen. ad lit. iv, 12): "If the ruling power of God were withdrawn from His creatures, their nature would at once cease, and all nature would collapse." In the same work (Gen. ad lit. viii, 12) he says: "As the air becomes light by the presence of the sun, so is man enlightened by the presence of God, and in His absence returns at once to darkness."
 

ficino wrote:

On EI, God's continual conservation of the thing at every moment is not needed because the thing is actual, so it by definition exists.

​That can't be right: if existence were in its definition it would of necessity exist. 

ficino wrote:

There is no thought that it will blink out of existence without continual divine operations to conserve it. DDC maintains that EI is false; EI maintains that DDC is false.

​EI can't do this though without attributing an absolute necessary existence to some physical thing or things, of which there is none, certainly in modern physics. The best you can do is assert this at a brute fact, which is a matter of personal belief or opinion and not science. I think, however, that people are attributing and confusing rather a relative necessity in this case; e.g., that because some house actually exists, therefore so does its matter (and matter generally) of necessity also exist.

ficino wrote:

So far I contend that Aquinas does not argue for DDC and does not seek to refute EI in the Five Ways. He does this elsewhere, in my view.

​I believe he effective does in the third way.

ficino wrote:

So arguments for the existence of God cannot justifiably appeal to premises that contain DDC.

​They can by reason of the necessity that some necessary thing exist to be cause of the existence of all contigently existant things, one; and two, that no physical thing contains in its definition existence and is, as a consequence, therefore only ever possibly existing and not necessarily existing. 

ficino wrote:

God's existence must be proved first,

​God's necessary existence can be demonstrated by the lack of necessary existence in physical things.
 

Last edited by Timocrates (1/09/2018 10:46 am)

@ Timocrates and bmiller:

Good points. I disagree with both of you on some things, have not made up my mind on others.

I was being too quick when I wrote the last sentence that bmiller quoted. As to 1), Aristotle and Aquinas both present the local movement of the simple bodies/elements as ultimately caused by the UM. I should have said that I am not yet convinced that their arguments succeed in showing that they are moved by the UM at every point along their transit. As to 2), it's very controversial in Aristotle.

I need to meet a deadline in two weeks. I hope to be back after Jan 22. I think it may be best, if we want to discuss the above stuff further, to have a thread on elements and ensouled beings and another one on EI vs DDC. 

Cheers, f

Yes, I also think it may all come down to whether one accepts brute fact or invokes the PSR.

Later, gents