Metaphysician Undercover, I have in mind by "possible being" something more like a "contingent being" rather than a being that is merely possible but not actual. Based on what I read, the reading of "possible" as meaning "contingent" that is "as what could have or could not have occurred/ existed" is consistent with Aquinas' use of the term "possible."

To summarize and condense, the argument I am suggesting as an interpretation of Aquinas' Third Way is as follows:

1. If everything is contingent, then it is possible for there to be nothing now.
2. But it is not possible for there to be nothing now.
3. Therefore it must be false that everything is contingent.
4. Therefore, there must be a necessary being.

To say a bit more, I think that Aquinas is not only rejecting that "there is nothing now." rather, he is in addition rejecting even the possibility that there is nothing now.

Thoughts? — NotAristotle

I would say that's a pretty simple, yet a fair representation. I think you are correct in your assumption that Aquinas rejects the possibility that there is nothing now. That proposition would not even make sense. What I said earlier, was that empirical evidence denies this possibility, but we also have arguments like Descartes'. So he starts with what we observe, contingent being (which excludes the possibility of nothing), and concludes that there must be also "necessary being".

I believe the point of the argument is that we observe the reality of contingent beings. The things we observe are contingent, and "contingent" in this context means dependent on something else, requiring a cause for its existence. The next point is that if there ever was a time when there was absolutely nothing, then there would still be nothing because there would be no cause as required to bring into reality these contingent things we observe.

The other necessary premise, which is not well stated is known as the principle of plenitude, sometimes exemplified by the infinite monkeys typing. The principle of plenitude states that if anything is possible, then if given enough time (the proposal of infinite time) it will become a reality. So Aquinas denies an infinite past with an infinite regression of contingent things, by applying this principle of plenitude, and assuming that if everything is contingent, then there is the possibility that at some time in the past there would be nothing, and by the principle of plenitude, there would have to have been such a time. These are the premises required to imply that not all existence is contingent.

1. We observe contingent beings.
2. if there ever was a time with nothing there would always be nothing.
3. By the principle of plenitude, if all beings are contingent beings then there would have been a time with absolutely nothing.

Well, it's on the right track, although it's highly truncated, isn't it? Agree that Feser's articles are useful on the subject.

Regarding potentiality and actuality, there's a Wikipedia entry on that here https://en.wikipedia.org/wiki/Potentiality_and_actuality

I'm interested in Aristotle's idea of 'potentia' as things which might exist, but are latent or potential until they're actualised. It describes the 'domain of possibility', which is different to things that can't or will never exist. See the article for further discussion.

I am going to be a bit argumentative here, and say, well whether you admit of an infinite sequence of contingents or not, we still have the problem that "now" is in the midst of those contingents. Get what I mean? Like, even if the contingents are not infinite in duration through time, "now" could be within the timespan of those contingents. That seems like a problem and it is a problem even if we only have a finite duration of contingents. It seems like a problem whether the principle of plentitude is recognized or not.

That is why I prefer an alternative interpretation of the argument. Instead of saying, "by the principle of plentitude there would be nothing now, therefore there must not be only contingents," I am saying, "the very possibility of nothing now requires the existence of only contingents...but this isn't a possibility...therefore there must be a necessary being."



Do you think there are any "necessary non-beings" ? A square circle perhaps.

I will let one of the logicians tackle that one!

I am going to be a bit argumentative here, and say, well whether you admit of an infinite sequence of contingents or not, we still have the problem that "now" is in the midst of those contingents. Get what I mean? Like, even if the contingents are not infinite in duration through time, "now" could be within the timespan of those contingents. That seems like a problem and it is a problem even if we only have a finite duration of contingents. It seems like a problem whether the principle of plentitude is recognized or not. — NotAristotle

I don't see the problem. The time referred to as "now" is in the midst of the contingents, that is described as what we observe, contingent beings. But it's not a problem to the argument, because if there ever was a time when there was nothing, there would be no contingents right now, because contingents require a cause, and nothing could not ever be a cause. That's what a contingent being is, one which requires a cause for its existence. So, the possibility of nothing is ruled out in this way.

That is why I prefer an alternative interpretation of the argument. Instead of saying, "by the principle of plentitude there would be nothing now, therefore there must not be only contingents," I am saying, "the very possibility of nothing now requires the existence of only contingents...but this isn't a possibility...therefore there must be a necessary being." — NotAristotle

I don't think your statement, "the very possibility of nothing now requires the existence of only contingents" is a coherent proposition. If there is nothing, then there is no contingents. So the possibility of nothing rules out the possibility of contingents, that's the point of the argument. "Nothing" and "contingents" are incompatible. That's what the third way demonstrates, but you make them compatible by saying that the possibility of nothing requires contingents.

This is because you've made "possibility" into a logical possibility, saying that nothing is logically possible because what we observe is contingent beings. But the argument denies the possibility of nothing, if there ever was nothing there would not be contingent beings now, so nothing is impossible. Aquinas is dealing with ontological possibility, as in Aristotle's "potential", like what Wayfarer mentions above. This is a sense of "possible" which is distinct from the modern usage of logically "possible".

As I said a contingent being is one whose existence is dependent on causation, it is caused to be. So prior to its existence it is merely "possible". It only comes into being if the appropriate efficient causes, the ones required to bring it into being, are initiated. In this way it is said to be a "possible" being, but this is an ontological possibility, meaning that the existent circumstances support the possibility of that being. This is other than logical possibility which just requires self-consistency.

I see what you are saying about contingents requiring an efficient cause. In fact, I think you are correct. However, I am not sure that that is Aquinas' argument in the 3rd Way. The argument for an efficient cause of an accidental series is covered in the 2nd Way I think.

because if there ever was a time when there was nothing, there would be no contingents right now — Metaphysician Undercover

-- unless nothing occurred at a time after now.

To your point about the incompatibility of nothing and contingents, allow me to rephrase.. how about "if there is nothing at any time (or even at all times) there could not be a necessary being; any beings that exist, if they exist at all, would have to be contingent beings."

And I think I am claiming the possibility of nothing in the same way that Aquinas does; that is, if all beings were contingent, there could have been nothing. The possibility of nothing is asserted within a conditional; I do not know enough about logic to know whether that makes it a logical possibility or not.

What I am claiming is that, were all beings contingent, it would be possible for there to be nothing at some (or all) times; and in particular, it would be possible for there to be nothing now (if everything were contingent). But, I contend that it is impossible for there to be nothing now. Therefore, by modus tollens, it cannot be the case that all beings are contingent. And therefore, there must be a necessary being.

However, I am not sure that that is Aquinas' argument in the 3rd Way. — NotAristotle

I'm quite sure that this is what he is talking about. If you read his expression of the third way you'll see that he says that what begins to exist only does so by being caused by something already existing. This is efficient causation, which we know as the active, or actual cause of existence of contingent beings.

-- unless nothing occurred at a time after now. — NotAristotle

This is incoherent, "occurred" indicates past time, so future is not relevant here.

To your point about the incompatibility of nothing and contingents, allow me to rephrase.. how about "if there is nothing at any time (or even at all times) there could not be a necessary being; any beings that exist, if they exist at all, would have to be contingent beings." — NotAristotle

I don't see how this is relevant. What Aquinas says is that we notice there is not nothing, we notice contingent beings. And, he concludes that it is impossible that there ever was nothing. So, by the observed existence of contingent beings, "nothing" is ruled out as impossible.

And I think I am claiming the possibility of nothing in the same way that Aquinas does; that is, if all beings were contingent, there could have been nothing. The possibility of nothing is asserted within a conditional; I do not know enough about logic to know whether that makes it a logical possibility or not. — NotAristotle

What Aquinas does is entertain the idea of "nothing" as what we would call a "logical possibility". We could say that Aquinas mentions "nothing" as a logical possibility, just like any suggestion which is not incoherent by self-contradiction could be said to be logically possible. But then he rules out "nothing" as ontologically impossible, and actually self-contradicting through reference to the material existence which we know and are familiar with.

In fact, what he shows is that your statement "if all beings were contingent, there could have been nothing" is incoherent, as self-contradicting. This is because he shows that if there ever was nothing there would always be nothing. therefore there would be no contingent beings. So, the existence of contingent beings appears to validate the possibility of "nothing", as Aquinas shows. However, this apparent validation is really nothing more than an illusion because if there actually ever was nothing there could be no contingent beings. So what he does here is demonstrate that "if all beings were contingent, there could have been nothing" is incoherent, as self-contradicting when all the terms are understood properly.

What I am claiming is that, were all beings contingent, it would be possible for there to be nothing at some (or all) times; and in particular, it would be possible for there to be nothing now (if everything were contingent). But, I contend that it is impossible for there to be nothing now. Therefore, by modus tollens, it cannot be the case that all beings are contingent. And therefore, there must be a necessary being. — NotAristotle

Yes, I think this is correct. If all beings are contingent, then nothing appears to be "logically possible". However, ontological reality shows us that there is something now, and this means, as you contend, "it is impossible for there to be nothing now". But you still need the rest of Aquinas' argument, to make your conclusion. You need to show that because the beings we notice now are contingent beings, it is therefore impossible that there was ever nothing. So "nothing" is impossible in a more absolute way. That is the impossibility which leads to the conclusion of "necessary being".

I might add that the third way extends beyond this point to show how an infinite regress of necessary beings is not possible, and finally this leads to the conclusion of "a necessary being".

First of all thanks for engaging in this discussion with me.

Second, I have the same objection that I voiced to Wayfarer; namely, Aquinas says: "Therefore, if everything is possible not to be, then at one time there could have been nothing in existence." If what you are saying about his argument is correct, surely he would have said "...then at one time there must have been nothing in existence." Yet that is not what he says.

Additionally, if your interpretation is correct, then the principle of plenitide is not actually doing any work. That is because by definition, according to your definition, all contingent things require a cause. In that case it doesn't matter how much time is involved.

Furthermore, I disagree with the definition of contingent you have deployed. I would define contingent here as "possible to be or not to be." If everything is contingent, then according to your definition nothing is contingent because nothing is possible to be (if everything is contingent). That seems contradictory.

Lastly, the argument I am suggesting is grounded in the law of noncontradiction. We both agree that contingent things exist now. I maintain that, to avoid contradiction, the contingent things existing now must exist now (but can not-exist at another time). But if something must exist now, then there cannot be nothing now. But if everything is contingent then there could be nothing now. However, there cannot be nothing now based on the law of noncontradiction. Therefore it must be false that everything is contingent i.e. there must be a necessary being

Second, I have the same objection that I voiced to Wayfarer; namely, Aquinas says: "Therefore, if everything is possible not to be, then at one time there could have been nothing in existence." If what you are saying about his argument is correct, surely he would have said "...then at one time there must have been nothing in existence." Yet that is not what he says. — NotAristotle

Well, continue in the context. He then says: "Now, if this were true, even now there would be nothing in existence, because that which does not exist only begins to exist by something already existing. Therefore, if at one time nothing was in existence, it would have been impossible for anything to have begun to exist; and thus even now nothing would be in existence--which is absurd."

So, he moves from "there could have been nothing" to "if at one time nothing was in existence... even now nothing would be in existence". Therefore he has demonstrated, as I said, that "nothing" is impossible, given the current conditions of contingent beings.

Additionally, if your interpretation is correct, then the principle of plenitide is not actually doing any work. That is because by definition, according to your definition, all contingent things require a cause. In that case it doesn't matter how much time is involved. — NotAristotle

I believe this is incorrect. There could be an infinite regress of contingent beings. That means an infinite amount of time with contingent beings causing the existence of other contingent beings. Isn't this the objection you made in the op, in the following passage?

An objection to Aquinas' argument, in my opinion, is that, while there could have been a time when nothing was in existence, there also could have been "possible beings" in existence at all times. In that case, the absurdity that Aquinas is suggesting need not occur. In other words, there is nothing absurd about all beings being "merely possible" beings. And in other words there need not be a necessary being. — NotAristotle

That is why the principle of plenitude is required. The principle of plenitude is not stated by Aquinas, and I don't think there even was a formalized version of it at the time, I believe it was just something which was taken for granted at the time, like a self-evident truth, outlined first by Plato. However, if you do some online research, you will see that analyses of the third way argument have determined that the principle is a requirement, for Aquinas to make the conclusion of necessary being.

This is because of objections similar to the one which you made in the op. There could have always been contingent beings, and never nothing, if "nothing" is only a possibility. So, the principle of plenitude is required to move from possible beings, and the possibility of nothing, to: there actually would have been nothing at some time, and so now there would also be nothing, therefore providing what we need to conclude necessary being.

Furthermore, I disagree with the definition of contingent you have deployed. I would define contingent here as "possible to be or not to be." If everything is contingent, then according to your definition nothing is contingent because nothing is possible to be (if everything is contingent). That seems contradictory. — NotAristotle

I don't know, I can't follow this at all.

the contingent things existing now must exist now — NotAristotle

I don't see how you derive this premise, and it isn't part of Aquinas' argument. Notice that Aquinas doesn't use "contingent" in the argument. So maybe we should leave that word out, as a distraction. What he says is that what we find are things which are possible to be, and possible not to be, because "they are found to be generated and to corrupt". Notice the temporal extension, of "generated" in the past, and "to corrupt" in the future. So your use of "now" is uncalled for.

It appears like what you are proposing is something like: "we notice that there are beings now, and what exists now must exist, therefore being is necessary. That's a nice simple argument, but it isn't Aquinas' argument.

It appears like what you are proposing is something like: "we notice that there are beings now, and what exists now must exist, therefore being is necessary. That's a nice simple argument, but it isn't Aquinas' argument. — Metaphysician Undercover

Yeah! That is essentially the argument. I would amend it just by adding "...and what exists now must exist [now]..."

And I think I can now better appreciate what you are saying about the principle of plenitude, but...

I don't see the problem. The time referred to as "now" is in the midst of the contingents, that is described as what we observe, contingent beings. But it's not a problem to the argument, because if there ever was a time when there was nothing, there would be no contingents right now, because contingents require a cause, and nothing could not ever be a cause. That's what a contingent being is, one which requires a cause for its existence. So, the possibility of nothing is ruled out in this way. — Metaphysician Undercover

I am not sure that my objection about "now" being at the time of contingents is fully met. The possibility remains that "now" is within the time span of an infinite sequence of contingents, and that the time of "nothing" will occur sometime after "now." But if that is the case then the infinite sequence of beings can all being contingent and there needn't be a necessary being; that is a problem for the argument and that is essentially the objection.

Yeah! That is essentially the argument. I would amend it just by adding "...and what exists now must exist [now]..." — NotAristotle

This is sort of like Aristotle's law of identity. Whatever exists [now] must be what it is, and not something else. This is expressed as the following necessity: "A thing is the same as itself". Notice though, that this relates to a thing's essence, what the thing is, which cannot be other than the thing's essence, what the thing is. But this principle has not been extended to a thing's existence, as you propose, and I believe it cannot be, for the following reason.

I believe that this is because the intelligible part of a thing, what we know of the thing, is its form, its essence, and "existence" is not understood as being part of the thing's form. In other words, we do not know what your statement means, to "exist now", it is unintelligible to us. In fact, the "now" changes as we speak. Therefore we cannot make the proposed statement, "it is necessary that what exists now exists now", because time has past between the first "now" and the second "now" such that they refer to different times which accordingly have different existents.

You might recognize that Aquinas described God as a being whose essence is His existence, and by that principle essence and existence are equated, even made to be the same, in God only. It is only in this special case that a thing's identity, what the thing is, (which is necessary in the sense that the thing cannot be something other than the thing which it is), is assumed to be the very same as the thing's existence. And this transfers the necessity of the thing's form, expressed by the law of identity, that it must be what it is, to the thing's existence, what it is, is that it is. And this makes "that it is" necessary by the law of identity. But that's only in the special case of God.

I am not sure that my objection about "now" being at the time of contingents is fully met. The possibility remains that "now" is within the time span of an infinite sequence of contingents, and that the time of "nothing" will occur sometime after "now." — NotAristotle

The contingents which you propose as occurring posterior to the time of now, in the future, have no existence. They are not real, and cannot be called beings, they are merely possibility. Therefore what you call "an infinite sequence of contingents" is not truly an infinite sequence, unless there is no beginning to it. If there is no beginning, then there is an infinite amount of time prior to now, and the principle of plenitude applies. If there is a beginning to the sequence, then there is not an infinite sequence, because it is limited by the beginning on one end, and now on the other end. In this case, the "necessary being" accounts for the cause of the first contingent being. It is "necessary", known by logical necessity, rather than being known as contingent.

But if that is the case then the infinite sequence of beings can all being contingent and there needn't be a necessary being; that is a problem for the argument and that is essentially the objection. — NotAristotle

You are proposing that the sequence of contingent beings has a beginning, in order to avoid the infinite time prior to now, and the principle of plenitude, which would indicate that in that infinite time there would be a time of nothing. But contingent beings must have a cause. If there is a first contingent being, one which is prior to all other contingent beings, it cannot have a contingent being as its cause, then its cause is necessary, and this is necessary being as distinct from contingent being.

You are proposing that the sequence of contingent beings has a beginning, in order to avoid the infinite time prior to now, and the principle of plenitude, which would indicate that in that infinite time there would be a time of nothing. But contingent beings must have a cause. If there is a first contingent being, one which is prior to all other contingent beings, it cannot have a contingent being as its cause, then its cause is necessary, and this is necessary being as distinct from contingent being. — Metaphysician Undercover

Not exactly, what I am proposing is this: First, let's assume that all beings are contingent only; that is, that there are no necessary beings. On that assumption, whether the principle of plenitude is applicable or not, but especially when it is applicable, the problem I articulated is salient. The problem is not that there are contingents posterior to "now." The problem is that there will be or may be nothing posterior to "now," that is, if we are still operating on the hypothetical assumption that everything is contingent only.

That is why I am forwarding the argument that I forwarded. But you mentioned an objection to that argument:

This is sort of like Aristotle's law of identity. Whatever exists [now] must be what it is, and not something else. This is expressed as the following necessity: "A thing is the same as itself". Notice though, that this relates to a thing's essence, what the thing is, which cannot be other than the thing's essence, what the thing is. But this principle has not been extended to a thing's existence, as you propose, and I believe it cannot be, for the following reason. — Metaphysician Undercover

I am not sure if the law of identity can be extended to a thing's existence either. Fortunately, I am not appealing to the law of identity; rather, I am appealing to the law of noncontradiction. In particular, I am appealing to what Aristotle says in De Interpretatione. The first sentence of Part 9 especially: "In the case of that which is or which has taken place, propositions, whether positive or negative, must be true or false." In other words, it must be true or false that something exists now, it cannot be both true and false.

And I would like to address the further objection you described concerning "now" --

In fact, the "now" changes as we speak. Therefore we cannot make the proposed statement, "it is necessary that what exists now exists now", because time has past between the first "now" and the second "now" such that they refer to different times which accordingly have different existents. — Metaphysician Undercover

I am not using now in a purely indexical sense. By "now" I mean this exact present moment. Which, in a few seconds will have become "then." Still, something must have existed in "that" moment.

The problem is that there will be or may be nothing posterior to "now," that is, if we are still operating on the hypothetical assumption that everything is contingent only. — NotAristotle

That issue becomes irrelevant when we consider what is prior to now, as Aquinas did. By considering what is prior to now we see that it is impossible that everything is contingent only. Therefore the "hypothetical assumption" has already been ruled out as incoherent in the way I described, through reference to what has occurred in the past. So applying that hypothetical assumption toward the future is pointless because it's already ruled out as incoherent through a proper understanding of the terms. When you say "there will be or may be nothing posterior to 'now,'" you are just carrying on with a proposed possibility which has already been proven to actually be impossible by being incoherent.

Fortunately, I am not appealing to the law of identity; rather, I am appealing to the law of noncontradiction. In particular, I am appealing to what Aristotle says in De Interpretatione. The first sentence of Part 9 especially: "In the case of that which is or which has taken place, propositions, whether positive or negative, must be true or false." In other words, it must be true or false that something exists now, it cannot be both true and false. — NotAristotle

I really do not think you will make any progress in this direction. Aristotle showed how it is the case that when potential is a part of the thing we are talking about, we must allow a violation to the law of excluded middle with respect to that potential. This is in relation to the future, things not yet decided. In the case of material things, their "matter" is that potential, so as Aquinas says, these things are possible to be and not to be, and this provides for "change", generation and corruption. So instead of violating the law of noncontradiction to deal with the possibility to be and not to be, under Aristotelian principles, matter, as potential, violates the law of excluded middle, because it neither is, nor is not.

You'll see that modern dialectical materialists (and dialetheists), following Hegel who actually rejected the law of identity, allow that the nature of matter defies the law of non-contradiction. This is a resolution to the problem of "potential" which Aristotle considered, but rejected, insisting that the law of noncontradiction must be maintained, and opting for a violation of the law of excluded middle instead, to allow for the reality of potential.

I am not using now in a purely indexical sense. By "now" I mean this exact present moment. Which, in a few seconds will have become "then." Still, something must have existed in "that" moment. — NotAristotle

This does not resolve the issue with "now". By this description, any proposed "exact present moment" as "now", is really a moment in the past, because by the time it is proposed as "now", it has passed. If you propose a future now, then it is not present, but future. The "now", as a point in time is not real because in reality, time is passing, and any proposed point in time will always be future or past. You could propose an extended period, or duration of time as your "now", but this duration of time would consist of change, and this destroys our capacity to truthfully say that there is such a thing (notice the static fixity of "thing") as what exists now.

So, when we look at "now", we are stuck with a duration of time. And, that duration of time consists of change, "becoming". Aristotle showed that becoming is fundamentally incompatible with the logical contraries of "being" and "not being", "is" and "is not". If we have state A (what is) at time 1, and state B at time 2, and change occurs between these two proposed points in time, then we need to describe this intermediary time, in order to understand change. If we propose a state C (what is) at time 1.5 as the intermediary, then we are left with having to describe the change between the initial state and the intermediary state, and between the intermediary state and the final state. If we propose more states of what is, in between, we just head for an infinite regress of states of being, without ever describing the actual "change" which occurs between the states of being.

This is the problem with "now". We like to represent it as a point in time, with a particular, describable "what is" which corresponds with that point of time. However, when the point in time is properly analyzed we find that it cannot ever adequately represent "now", as we know and understand "now" in lived experience, as it always ends up being in the past, or a projected point in the future. So we find out that "now" really consists of a duration of time. The duration cannot be entirely in the past, or else it would be past time, nor can it be entirely in the future. Therefore the duration which we call "now" must consist of both past and future. Furthermore, there is a substantial difference between past (as what is fixed, determined, and necessary), and future (what is indeterminate, not fixed, and possible). Since both of these somewhat opposed. and incompatible aspects of reality exist at the very same time, "now", the question of "what exists now?" is itself incoherent.

you are just carrying on with a proposed possibility which has already been proven to actually be impossible by being incoherent. — Metaphysician Undercover

How is the proposed hypothetical possibility impossible by being incoherent?

I really do not think you will make any progress in this direction. — Metaphysician Undercover

I did not see where the objection was in these two paragraphs.

This does not resolve the issue with "now". — Metaphysician Undercover

Okay fine, let's forget about "now" and say instead that any moment in the past must have been. I will reformulate my argument:

1. If everything is contingent, then there could have been nothing in the past.
2. But there couldn't have been nothing in the past, something having already existed in the past.
3. Therefore (by modus tollens) it must be false that everything is contingent.
4. Therefore there must be a necessary being.

Although I really do think Aquinas meant "now" as I do, in the colloquial sense, not in the technical sense you have described. Otherwise, wouldn't the objection you stated concerning "now" be a problem for Aquinas too?

How is the proposed hypothetical possibility impossible by being incoherent? — NotAristotle

By the nature of "contingent being", it is shown that it is impossible that "all being is contingent" by Aquinas' argument. Therefore the hypothesis "everything is contingent only" is rendered incoherent.

Okay fine, let's forget about "now" and say instead that any moment in the past must have been. I will reformulate my argument:

1. If everything is contingent, then there could have been nothing in the past.
2. But there couldn't have been nothing in the past, something having already existed in the past.
3. Therefore (by modus tollens) it must be false that everything is contingent.
4. Therefore there must be a necessary being. — NotAristotle

I don't see how the necessity of the premise (2) "something existed in the past" is supported, when (1) explicitly says there could have been nothing in the past. That is the point of Aquinas' layout, it shows how (2) which contradicts (1), rendering the primary hypothesis "everything is contingent", as incoherent, is derived.

Although I really do think Aquinas meant "now" as I do, in the colloquial sense, not in the technical sense you have described. Otherwise, wouldn't the objection you stated concerning "now" be a problem for Aquinas too? — NotAristotle

There is no need for Aquinas to elaborate or clarify his use of "now" because he does not use it to distinguish between past and future. You made that distinction in your argument, so this left you open to that criticism.

By the nature of "contingent being", it is shown that it is impossible that "all being is contingent" by Aquinas' argument. Therefore the hypothesis "everything is contingent only" is rendered incoherent. — Metaphysician Undercover

But that is the problem isn't it; Aquinas' argument as you have stated it does not go through if there could be nothing posterior to "now." If there could be nothing posterior to "now" it could be the case that everything is merely contingent.

I don't see how the necessity of the premise (2) "something existed in the past" is supported, when (1) explicitly says there could have been nothing in the past. That is the point of Aquinas' layout, it shows how (2) which contradicts (1), rendering the primary hypothesis "everything is contingent", as incoherent, is derived. — Metaphysician Undercover

But (1) does not explicitly say there could have been nothing in the past; it says "if everything is contingent, then there could have been nothing in the past." It's a conditional statement, that is it. And that is basically what Aquinas is doing too, he is entertaining, in the same way a conditional does, the possibility that "everything is contingent."

There is no need for Aquinas to elaborate or clarify his use of "now" because he does not use it to distinguish between past and future. You made that distinction in your argument, so this left you open to that criticism. — Metaphysician Undercover

But the original argument I formulated (1-4) does not make use of the past or future, rather it only discusses the present, so again I am not sure how my use of "now" is different than Aquinas'.

But that is the problem isn't it; Aquinas' argument as you have stated it does not go through if there could be nothing posterior to "now." If there could be nothing posterior to "now" it could be the case that everything is merely contingent. — NotAristotle

I don't think that's relevant. If everything is contingent, then there would be an infinite regress of contingent beings prior to now, implying infinite time prior to now. However, "all being is contingent" implies the possibility of nothing. And, by the principle of plenitude there would have been a time of nothing. If there was a time of nothing prior to now, there would still be nothing. Therefore "all beings are contingent" is incoherent.

But (1) does not explicitly say there could have been nothing in the past; it says "if everything is contingent, then there could have been nothing in the past." It's a conditional statement, that is it. And that is basically what Aquinas is doing too, he is entertaining, in the same way a conditional does, the possibility that "everything is contingent." — NotAristotle

Right, and by the principle pf plenitude, if everything is contingent there would have been a time in the past with nothing. And, since "contingent being" implies that a prior cause is necessary for the being's existence, if there ever was nothing, there would always be nothing after that time. Therefore "everything is contingent" is incoherent.

prior to now — Metaphysician Undercover

That is the crux of the matter. The problem for the principle of plenitude is not when nothing is prior to now; the principle handles that objection well. The problem is when nothing will occur (or may occur) after now. That's the objection I am stating. Do you see why I think it is a problem for the argument you stated?

The problem for the principle of plenitude is not when nothing is prior to now; the principle handles that objection well. The problem is when nothing will occur (or may occur) after now. That's the objection I am stating. Do you see why I think it is a problem for the argument you stated? — NotAristotle

No, I don't see how it could be a problem. Since "all being is contingent being" implies an infinite regress of causation, therefore an infinite amount of time prior to now, nothing would have already occurred, prior to now, by the principle of plenitude. This makes your reference to "after now" irrelevant.

Since "all being is contingent being" implies an infinite regress of causation, therefore an infinite amount of time prior to now, nothing would have already occurred, prior to now, by the principle of plenitude — Metaphysician Undercover

And would you say the nothing that occurred happened after all the contingent things passed away, or would you say the nothing occurred before the contingent things were generated?

The nothing did not occur, that's the point of the argument. If nothing did occur then there would still be nothing today. But if everything is contingent nothing would have occurred. Hence the conclusion of necessary being.

If all things are contingent then there would have been nothing at some time in the past (by the principle of plenitude). If there was nothing at some time in the past there would still be nothing now. There is not nothing now, there is contingent being. Therefore the proposition "all things are contingent is incoherent", and there is necessary being.

Therefore the proposition "all things are contingent is incoherent", and there is necessary being. — Metaphysician Undercover

Right. I am asking you: "if everything is contingent, would there have been nothing today because there would have been nothing after all contingent things existed, or because there would have been nothing before all the contingent things began to exist?"

I think the point is simple. If the proposition "Everything is contingent" is true, then there is always nothing. The proposition "After all contingent things existed" is eliminated as meaningless because there would never be any contingent things.

Oh I see, so then you are saying that there would have been nothing today if everything were contingent because there would have been nothing before any contingent things and that that nothing would have prevented all the contingent things from existing entirely. Do I have that right?

That's right. "Everything is contingent" implies two things, the possibility of nothing, and infinite regress. Infinite regress implies infinite time which with the principle of plenitude realizes the possibility of nothing. The reality of nothing denies the possibility of any contingent thing. So "Everything is contingent" is self-refuting, incoherent, because what it actually means is that it is impossible that there is anything.

Time has nothing to do with it though, so the principle of plenitude is not doing any work in your argument. Not to mention, you are describing Aquinas' Second Way: if everything is contingent and contingent things require a cause, then there would be nothing because nothing would cause all the contingent things (even if there were an infinite number of them); that is approximately the Second Way.