Complete essay on-line: http://www.asa3.org/ASA/PSCF/1995/PSCF3-95Cramer.html
Pdf download (17 pages): http://www.google.com/url?sa=t&rct=j...AiJCVwEIuYM1FA

Below is the basic introduction that is followed by critiques and commentary from cosmology and philosophy.
Introduction:

Adler's Cosmological Argument

In 1980, Mortimer J. Adler published an interesting little book titled, How to Think about God.1 He subtitled it "a guide for the 20th-century pagan" and immediately appended a footnote to the subtitle defining a pagan as someone who does not worship the God of Christians, Jews, or Muslims. In the book, Adler critiqued traditional proofs for the existence of God as a springboard for presenting his own variation of the argument from contingency.

The philosophical asides on the French existentialists, the errors of Immanuel Kant, and the fads of theological and philosophical thought alone make the book enjoyable and worthwhile reading. The main argument, however, is of considerable interest in its own right. Moreover, many relevant developments have occurred since the publication of the book that, I believe, strengthen his case. Therefore, it seems appropriate to reconsider and extend his arguments and considerations.

The first move Adler makes is to discount the possibility that the cosmos had an absolute beginning. He does not argue the cosmos has existed forever; he explicitly assumes so. The reason for this move is that if the universe truly had an absolute beginning, it was made from nothing. In Adler's words, it was "exnihilated." But, an exnihilated cosmos implies "... that God, the exnihilator, exists."2 Therefore, Adler is compelled to assume an eternal universe to avoid creating a circular argument for the existence of God.

Starting with an eternal cosmos, Adler also rejects attempts to argue for the existence of a first cause of the cosmos, which would, of course, soon turn out to be God. With a universe stretching back into an infinite past, an infinite series of causes without terminus is just as possible as the eternal universe he has just assumed.

The basic premises of his argument derive from the traditional argument for the existence of God based on the existence of contingent entities (which Adler calls "the best traditional argument"). He lists these premises as follows:

1. The existence of an effect that requires the operation of a coexistent cause implies the coexistence of that cause.
   
2. Whatever exists either does or does not need a cause of its existence at every moment of its existence; that is, while it endures, from the moment of its coming to be to the moment of its passing away.
   
3. A contingent being is one that needs a cause of its continuing existence at every moment of its endurance in existence.
   
4. No contingent being causes the continuing existence of any other contingent being.
   
5. Contingent beings exist in this world and endure, or continue in existence, from the moment of their coming to be to the moment of their passing away.

If these premises are true, it then follows that a noncontingent being must exist that continues the existence of those contingent beings we most certainly know exist. That is, a necessary being exists and holds all else in existence. The necessary being can only be the supreme being, God.

However, Adler judges the third premise probably false and the traditional argument for the existence of God from contingency a failure. The judgment is based on the observation that the contingency we observe in the universe is superficial, involving only transformations. Radical contingency, involving exnihilation and annihilation of entities, if it occurred, would call for a different conclusion. Adler also judges the third premise false because it is plausible that contingent beings, once generated, can indeed continue to exist on their own until some cause proves their contingency by causing them to cease to exist. Adler cites the way the inertia of an object continues the motion of the object and suggests an "inertia of being" may exist to continue existence and falsify the third premise.

Taken together, these ideas show that it is reasonable to reject the argument from contingency. That is, the argument does not lead inexorably to the conclusion that God exists. It might be true but one is not compelled to accept it. Rejection is intellectually respectable.

At this point, Adler recasts the argument. While he regards the third premise as implausible concerning particular entities in the universe, it might be true of the universe as a whole. The entire universe might be radically contingent though no part of it is radically contingent. What is true of the whole is not always true of the parts. For example, the set of all counting numbers is infinite but no one counting number is infinite. Adler argues that the cosmos as a whole is radically contingent.

The argument has two steps. He first notes that the present universe is only one of many possible universes. The long standing discussions among cosmologists about the type of universe we live in are ample evidence of the plausibility of this step. If cosmologists have not reached a conclusion, then the question is open and the possibility of other universes is a reasonable consideration. Do not misunderstand here. Adler needs only the logical possibility that the universe might have been other than it is. Physical actualization of the possibility is irrelevant to the force of the argument. Indeed, the existence of other universes confuses the argument by confusing the meaning of the term universe. Granted that the present universe is not the only possible universe, it then follows that the present universe has only possible existence; it does not have necessary existence.

The second step is to note that whatever might be otherwise might not exist at all. Anything that necessarily exists must be exactly what it is; it cannot be other than what it is. The converse is also true thenówhatever can be otherwise does not exist necessarily and must be able to not exist. However, for the cosmos to cease to exist, it must be annihilated and not merely transformed.

Another way of arriving at the same conclusion is to rely on the principle of sufficient reason. Anything that exists does so because there is sufficient reason for it to do so. The cause that is the sufficient reason may reside either in the thing or in something else but the cause must exist. For a merely possible entity, the sufficient reason cannot reside in the entity but must reside in another. If the universe is merely possible, then the sufficient reason for its existence resides not in the universe but elsewhere. But the universe is all of the physical reality so the merely possible existence of the universe points "outside" the universe to the existence of a nonphysical reality.

Adler concludes then that, by the previous premises, there exists a necessary supreme being so that the universe stays in existence. God must be there to sustain the universe even if the universe is eternal. Beginning by rejecting belief in a creating God, Adler finds evidence of a sustaining God. The existence of a sustaining God, however, then becomes grounds for asserting the creating activity also. Thus, the idea of a created universe with a beginning (and, likely too, an end) now becomes more plausible than the idea of an eternal universe.

Adler regards his argument as showing beyond reasonable doubt that God exists. He does not claim certainty for the argument.

I don't see the point in these. If X makes it likely that God exists then; if we assume X, it is likely that God exists.

I think I prefer the ones who go "I just know in my heart".

This argument is invalid. It does not follow from the possibility of universes different from the one we live in that the one we live in isn't necessary unless we also assume that there can be only one universe.

Also, his inference from the fact that scientists argue about the nature of the universe to the possibility that the universe could be other than it is is questionable. For instance, mathematicians and logicians also have such arguments, but this doesn't mean that the correct answer, once found, would not be regarded as following necessarily from the axioms.

Here what we have is an intuition: There must be an unmoved mover, uncaused causer, etc. If you have this intuition in a strong way, then fine, posit such a thing. However, this only tells us the bare fact that there must be some thing, not what it is. For all we know, the uncaused causer might be some elementary particle. It might be our Aunt Sally. Since all we have shown (assuming you accept this intuition) is the bare logical necessity of such a thing, once we have it, then the argument is over.

Here tame deuces is right. If you assume that there is some reason why everything exists then of course you'll find that there must be some reason why the universe exists. Calling it "The Principle of Sufficient Reason" makes it sound big and special, and something we have to accept on other grounds, but we really don't.

Lol. I don't see how any modern philosopher (which, to be fair, probably isn't the best way to think of Adler) can reasonably make the Thomistic "and this all men call God" move. The necessary "being" if shown to exist by this argument has not been called God by all men since at least Spinoza (well, okay, maybe Spinoza called it God, but not in a way that Aquinas would recognize).

I think the author covered your objection with his supporting arguments. At least with the prevalent theory in cosmogony, that the actual universe is ‘possibly actual’ and not necessarily so.

http://www.asa3.org/ASA/PSCF/1995/PSCF3-95Cramer.html
Modern cosmology must be judged to be supportive of Adler's argument to the extent it seriously countenances the possibility of many types of universe. Ironically, the significant degree of enthusiasm in current cosmology for other worlds arises from exactly the opposite intent. Most of the advocates of the existence (or possible existence) of other worldsóother parts of the universeóare very clearly motivated to deny the uniqueness of this part of the universe. They want to avoid explaining that uniqueness and readily perceive that the possibility of other worlds conveniently obscures that uniqueness.

There are many serious versions of many worlds theories. An early one, the Everett many worlds theory, was derived not from cosmology but from an effort to understand quantum theory. A more recent one is J. Richard Gott's inflationary model of our universe as one of many inflated bubbles. Whether any of these is true is not particularly important. What is important is that the variety and present health of these ideas makes plain there is no reason now to suppose the whole universe is necessarily what it is. The consensus of cosmologists is that the universe out there has the contingency Adler needs for his argument.

Any cosmological argument needs to make that leap, so if you reject doing so, you’re just objecting to the inductive nature of the argument. In other words, if you disallow the theist to distinguish between a necessary cause (like say a quantum vacuum) and God as an uncaused cause, you’re conflating a brute fact with something that it’s own cause for existing. Which again is just a dismissal of cosmological arguments in general, not a rebuttal against this argument in particular.

Sure, but you can only reach that conclusion after first rejecting the principle of sufficient reason, without which the theist can’t possibly advance a cosmological argument. At some point there’s a line between an emanating being (like Plotinus’ conception of The One) or perhaps a deist sort of god and the more volitional/teleological accounts of God that Christians hold. So, if you're not willing to grant the theist the means to put forth his argument and employ the terms as he defines them, you're not really countering his argument, you're just saying he can't make it.

My counter was directed towards both of the points you bolded. His reasoning is incorrect--it doesn't follow from the possibility of alternative universes that the actual universe is not necessary unless there can only be one universe. And second, the inference from the existence of different cosmological theories to the contingency of the universe seems unwarranted unless he is willing to grant the same contingency to mathematical and logical claims. If he is simply asserting that there is a consensus among cosmologists that the universe is contingent, fine. I am not familiar enough with the field to know whether he is correct.

It's not that I am disallowing the theist from doing anything, it is only that I am pointing out the limits of the argument. The notion of an uncaused cause doesn't tell us what the causer is, just that it is not itself caused. What it is would seem to me to be an empirical question, and the attempts of philosophers to describe it through a priori reasoning just seems pointless to me.

As for rejecting cosmo arguments in general, I'm fine with that. I don't see anything particularly innovative here, and so am rejecting this argument for the same reasons I reject Leibniz's version.

I feel like you are working yourself around to again telling the atheist that he is begging the question because he rejects the premises of the argument made by the theist. So yeah, I don't accept the Principle of Sufficient Reason. However, I don't do so for circular reasons, but just because it seems to me a huge and unwarranted assumption about reality with insufficient evidence supporting it. So your claim that I'm not countering the argument by rejecting it is false.

Well, the existence of the universe is not (logically) necessary, since its non-existence is (logically) possible. Hence, the proposition ‘the universe exists’ is possibly true and possibly false. From which, since there is a (logical) possible world in which the proposition is true AND a possible world in which it’s false, it follows that the proposition is logically contingent. In other words, p ‘the universe exists’ and ~p ‘the universe doesn’t exist’ are both logically contingent propositions, it’s just that p is true and ~p is false.

So I think you’re confusing the author’s attempt to show how modern cosmology agrees with the proposition with the philosophical establishment of the proposition. The latter, seems to me at least, clearly established.

How is that not just a rejection of inductive reasoning? I mean the premises obviously support (though not conclusively) the conclusion, so if we make it that far into the argument one or the other is true. From there if you won’t let the theist plead his case against say a brute fact existence, a deist god or whatnot all you’re doing is just dismissing the argument because it doesn’t meet your criteria of certitude.
Sure, that’s your opinion. However, the principle is well enough accepted in the philosophical community and in fact is the driver of scientific enquiry so no one is really compelled to accept your take on the issue.

How do you know that it is logically possible that the universe doesn't exist? Are you relying on the conceivability criterion here? I mean, I don't believe that it it is necessary that the universe exist, but I don't believe that it is not necessary either--this is just one of those things that I don't know and don't really know how I would come to know on the basis of our current limited knowledge of the universe. The linked argument gave a couple of reasons for thinking that it was not necessary that the universe as a whole exist and I showed that neither of those reasons were very good. You seem to just be assuming it here.

I don't understand what you mean in your last paragraph.

First, I'm not conflating brute facts with uncaused causes--although I would point out that a brute fact is a species of uncaused cause. I haven't actually said anything about at all about "brute facts." You seem to be assuming that I mean this when I talk about the possibility of an elementary particle that is an unmoved mover, but I don't. I mean that I think that a self-caused causing elementary particle would function just as well as a self-caused causing God. All the cosmo argument gives you if correct is the self-caused causer--it doesn't tell you that it must be a mind or all the other stuff that goes along with being a God.

I suspect that the real disagreement between us here is that you accept some more Aristotelian account of causation and I accept Hume's. Most relevantly, I suspect that you are making assumptions about the necessity of teleology in our account of nature that I will reject.

Second, telling me that the inductive inference here is "obvious" won't do much to convince me. Evidently I don't find it so obvious myself. In fact, it seems to me that a universe as a whole is different enough from the things within that universe that I am not confident that it will have the same characteristics, such as having a reason for existing or being the way it is. And I'm even more skeptical of the ability of our limited intellects of being able to accurately reason our way into knowing what this reason would be if it existed.

Yes, it is my opinion. I am part of an empirical, naturalistic tradition in philosophy wherein it is typical to reject the principle of sufficient reason (and I certainly don't regard it as "the driver of scientific enquiry."). This isn't unique to me--you see Hume making many of the same points that I have. But yeah, if you want to just ignore those who reject the PSR, then fine, obviously my own views are just sort of left out of this discussion.

I am a bit confused as to what you think the point of this argument is. You say that no one is really compelled to accept my take on the PSR. Shouldn't you be more worried about whether anyone is compelled to accept yours? I don't think that my rejection of this argument shows that God doesn't exist. Rather, I think it is just a matter of showing that the argument fails to provide a reason for those who don't already accept the existence of God to do so. But you seem to have a different end in mind...

Holy crap, there's more actual philosophy in RGT than SMP.

(p) the universe is in existence.
(~p) the universe is not in existence.

p is necessary iff ~p is not possible.

Based on what we know, I’m okay saying that the universe came into existence roughly 14 billion years ago, so, possibly ~p. Or, I think most cosmologists agree that the universe will burnout or cease to exist at some distant time, so again, possibly ~p. Hence, I don’t think the proposition ‘necessarily p’ is warranted at all.

So if one accepts the above, then one agrees that p is possibly true and possibly false, hence, p is a contingent proposition. From which it follows that the universe’s existence is contingent on some cause outside itself for every moment of its 'actual' existence.

That’s pretty much it and I think the argument is pretty solid up to that point. Granted the argument then takes on a speculative tone, but I think it’s important to note that whatever that cause (some cause outside itself) may be it is "wholly other" than anything we’re currently familiar with or are aware of. Hence, it’s not out of line to consider or posit a non-naturalistic cause because there’s no naturalistic cause we’re aware of that is really a counter-fact to consider, i.e. any naturalistic posit is equally as speculative as a non-naturalistic posit. Put another way, while Adler’s argument may be speculative it’s no more speculative than the latest books by Stephen Hawking and Brian Greene. The latter being naturalistic speculation, the former non-naturalistic and/or theological speculation.

Speculative is overstating it. Speculative can be taken to mean "based on theoretical constructs" yes, but in science even theoretical constructs have to hold predictive power and be falsifiable... and even though examples exist where falsifiability is still not attainable, atleast there is rigor applied. In physics they're just (to simplify a bit) mathematical bridges between two (or more) phenomena which might or might not be indicative of mediating phenomena.

If we are to apply the word speculative here, we have to put the word "merely" in front.

To claim this essay speculates no more than pop science books by fairly esteemed theoretical physicists and cosmologists is, to be brutally honest, nonsense. This essay isn't based on a single quantifiable thing and certainly not on any kind of model with rigor except by naming a few and basically stating "they are not absolutes". It seems more based on a dictionary and conclusion that was likely typed (atleast mentally) in advance.

The essay is just offered in support of Adler’s argument. Below is Adler’s argument the way he framed it along with his critique and justification for accepting it. So perhaps you can point out precisely where Adler goes off the rails of reasonableness.

(As a bit of an aside, this whole issue with possible worlds, multi-verses along with what falls under the banner of strict naturalism or science proper is a terminological mess. For example, I think of the natural world or naturalism as composed of exactly one universe and precisely three spatial dimensions and science proper as dealing with the observable and verifiable (as opposed to mathematical modeling). So, to me at least, multiple dimensions and universes don’t fall under the heading of strict naturalism. However, since math and physics are involved with modern cosmogony once the argument leaves our universe and three dimensions I think of it more as supra-naturalism as opposed to the theological definition of super-naturalism, which is primarily logical conjecture.)

http://www.themoralliberal.com/thera...t-idea-of-god/

Let me repeat the argument again for you now. If the existence of an effect implies the existence of its required cause and if contingent things exist and if everything contingent must be caused to exist and if no contingent thing can ever cause the existence of another contingent thing, then it follows that a necessary being exists as the cause of the existence of the contingent things known by us to exist.

Does this argument which I’ve just been expounding to you by means of these diagrams prove the existence of God conceived as the Supreme Being and therefore as a necessary being? Let me say it once that it would prove the existence of God if all the premises in the chain of reasoning could be known by us or asserted by us as true. If all those ifs that I stated in that chain of the argument could be asserted as really true, then I think the person who asserted them as true would be entitled to say he knew God’s existence as the conclusion of a rational process of proof or inference.

Now philosophers and theologians differ about this. Some philosophers and theologians think that we can assert all these premises as true and therefore that we can know by our reasoning that God exists. Other philosophers and theologians doubt, very seriously doubt that we can assert the truth of these premises and therefore they think that we are in grave doubt, as far as our own natural knowledge goes, about God’s existence.

Now my own view here is neither the one nor the other of these two extremes. I think of the four premises or propositions that constitute the body of the argument, I am clear and certain about two of them. I am clear that contingent things, things like you and me or trees and stone, that such things exist. I am also clear that if the effect exists, the cause required for its existence must exist. These two things I’m clear about. But when I come to the proposition that contingent things need a cause of their existence, I have some difficulty understanding that because I’m not sure I know the difference, really understand the difference between cause of existence and cause of becoming. And the most difficult proposition of all for me to understand is the proposition that contingent things cannot cause the existence of anything, they can only cause the motion or change or becoming of things but not the existence of anything.

Now I think that some people are better able to understand these matters than I am. And for people who can understand them better than I, think it is fair to say that they in their understanding really understand and know the truth about God’s existence. I would go so far as to say that even for persons like myself with a weaker understanding of the truth of these propositions, I have some rational grounds for a certain that God exists even though I have to make a leap, a leap beyond those rational grounds to a belief. My reason carries me just so far being weak. My understanding doesn’t carry me the whole way yet. My understanding and reason carry me far enough so that I’m entitled as a rational man, as a reasonable man am entitled to make a leap beyond reason to the belief that God exists. And when I make this leap, I think I make it not to a belief in the God of the philosophers but I think the God I believe to exist is the God that is worshipped by the religions of the West. As Pascal says and other philosophers, “The God of Abraham, Isaac and Jacob.”

Okay, the criterion you are using here to determine whether something is contingent is whether they started to exist. I guess the idea is that whatever started to exist might have not existed. For instance, it makes fairly clear intuitive sense to say that I started to exist some 32 years ago. And, if my parents had never met, or not been in the mood, or any number of other things had happened I would not exist. Thus, it seems like we have good reason to think that it was not necessary that I exist.

However, none of these considerations apply to the universe as a whole. First of all, while it is true that according to some cosmological theories the universe "began" to exist with the big bang, since time itself is part of the universe, this is a very different idea of "beginning to exist" as compared to myself. For instance, there would be no time during which the universe did not exist. There wasn't a point in time during which the universe began existing. Insofar as our notion of "began" implies a before, I am not even sure that it would be accurate to make this claim.

Second, we know what kind of things go into causing humans such as myself to exist, but we don't know what goes into causing universes to exist. Thus, we can suppose that if the starting conditions were different, which seems possible if anything is possible, then I would not have existed. However, we don't know what the starting conditions for the universe are, or whether they could be different than they were. In fact, that is explicitly the claim of the theist, that the nature of the starting condition (God) is such that it couldn't be different than it is. My claim is that if the theist is willing to accept this about God purely as a postulate of reason, then I don't see why she shouldn't be equally willing to accept it for other non-god like things.

I would still like an answer to this query:

Above you seem to admit that your answer is speculative (mostly speculative?). I would admit that we currently don't know what, if anything caused the universe to exist, and so I would agree with you--as I think they would as well--that the answers provided by scientists such as Hawking and Green are also speculative (although like tame_deuces I think of a more fruitful variety than the kind you are using). As such, I don't think they provide reason for believing in the existence of such objects as are necessitated by those speculations. Naturally, I think the same about your speculation. So what then is the purpose of this argument?

(p) the universe is in existence.

Since the negation of p is not a violation of the law of contradiction or a contradiction in terms, p is not a necessary proposition (or ‘necessarily p’ is false). And since it’s conceivable that the universe is either in existence or not, i.e. there is a possible world where the universe is in existence and a pw where the universe is not in existence: possibly p and possibly ~p. From which: if possibly p and possibly ~p and if the universe is actually in existence, then it is contingently true that p and contingently false that ~p.

Adler’s point is that while it is true that every necessary proposition is possible, it is also true that no necessary proposition is contingent and as a consequence no contingent proposition is necessary. Hence, if p is contingently true then p is not a necessary proposition, or ‘necessarily p’ is false, from which it follows that ‘possibly ~p’ is true. And since the universe actually exists, ‘possibly p’ is true.

Now I think where we’re reading his argument differently is that somehow you’re taking the above as an argument for the universe having a beginning, while I’m not. I think you can get there from the above, but my reading of his argument is that he’s essentially claiming that if ‘contingently, the universe exists’ is true, then there must be (or it’s reasonable to suppose that there should be) a ‘supportive’ cause or a sufficient logical/metaphysical reason why the universe is continually kept in existence or a cause/reason why the universe ‘durates’.

So, to me, the difference between Adler’s argument and say the Kalam argument is that the latter fails if the universe’s duration is infinite, while Adler’s does not. In other words, whether the universe technically began to exist or not doesn’t negate its contingency, and hence, the universe’s continual need of a supportive cause/reason to exist/durate. And I believe that holds regardless of whether or not we treat the universe as an actual whole or a composite whole.


As a bit a preface, I treat philosophical arguments for God more as justifiers of belief rather than providing any significant compulsive force to accept the existence of the “God of Abraham.” With that said and with what I highlighted above as the difference between Adler’s argument and the Kalam, what I think this particular argument establishes is that the universe is in need of a necessary cause to continually exist. Now I’ll grant you or others the point that this argument, without the support of any other theological beliefs, assumptions or arguments, doesn’t get us any nearer to determining whether that necessary cause is simply a necessary cause or a necessary being. However, by getting to that point I think this particular argument helps the theist in presenting his case that a naturalistic necessary cause (or what I term a supra-natural necessary cause) is just as speculative as the theist’s supernatural cause.

Here you provide two different arguments for the claim that p is not necessary. First, you argue that the negation of p is not a contradiction and so p is not necessary. Second, you argue that since we can conceive of a possible world where p is false, p is not necessary.

Now, with regards to the first argument I have two responses. First, I'm not sure that it is a necessary criterion of a necessary truth that its negation be a contradiction. Second, and more importantly, I think it is epistemically possible that the negation of p is a contradiction.

With regards to the second claim, while I agree that it seems like we can conceive of a possible world where p is false, this would only be true if p is in fact not necessary. In other words, if "necessary existence" is coherent, then just as with Plantinga's ontological argument, the fact that we can conceive of God (or the universe) as not existing doesn't show that God (or the universe) doesn't necessarily exist. Thus, conceivability as a sufficient condition for a proposition being contingent fails with regards to existence claims.

I'm not reading Adler's argument as a kalam argument, but rather as akin to the Leibnizian cosmo argument. In other words, I think it is pretty much like this argument, (with my responses being here). I understood the reference to a beginning to the universe as providing evidence for the claim that p is not necessarily true and so the universe requires some external cause for its existence.

Sure, I get this, it is possible that an eternally existing object is contingent.


I find the bolded confusing. How is it that an argument can justify your belief that p while at the same time not providing any significant compulsive force for p being true? I can see how this is the case with regards to pragmatic arguments such Pascal's Wager, but not with the traditional five ways type arguments.

The reason I ask the question is this: You say that you think that this argument establishes that universe is in need of a necessary cause to continually exist. Now, as I've said in response, I don't think this argument establishes any such thing. Rather, it assumes it by including the PSR as one of its premises. Instead, the point of this argument seems to be the claim that the universe cannot be the cause of its own existence. And again, this seems to be based on various assumptions that are being made either about how we define or understand "universe" or about the nature of the first cause, etc.

Now, I don't think I have any good reason to think those assumptions are false. But neither do I think any particularly good reason has been given to think they are true. Thus, I don't really see how we've advanced much by this argument in increasing the likelihood that the claim that god exists is true. So, what's the point? Why not simply assert, "God exists," and be done with it?

I think they’re inter-definable. Starting with the narrowly logical necessary ‘a is a’ its negation ‘a is ~a’ being a logical contradiction is impossible. With the broadly logical necessary ‘a bachelor is not a married man’ its negation along with the definition of the terms is a logical contradiction in terms and likewise impossible. So if you’re thinking they’re not inter-definable and a proposition's negation is not a necessary criterion, I’m failing to see what you mean.

If one lacks the definition of a bachelor, then ‘possibly, a bachelor is a married man’ can be asserted on epistemological grounds. So, I’m guessing you’re saying something like the term ‘universe’ is undefined. Now I’m a little handicapped without your criteria for a necessary proposition, but I think you’ll need a supporting argument like below to support such a position.

A universe is such that it could not possibly fail to exist.
There is an actual universe.
Therefore, the actual universe could not possibly fail to exist.

What (r) ‘the multiverse proposal’ claims is that reality is such that a universe such as ours could not possibly fail to exist, because every actually possible universe obtains. So, the truth of the proposition…

(q) the universe cannot possibly fail to exist.

… is contingent upon the truth of another proposition r, which is to say that q is contingently true if true. And since a contingent proposition cannot be necessary, ‘possibly, the universe could fail to exist’ is not necessary and you’re back to not being able to claim: that ‘possibly, the universe doesn’t exist’ is false.
I’m not saying that conceivability is a sufficient condition to establish contingency. What I’m saying is that conceivability establishes logical possibility; actuality establishes contingency. For example, ‘possibly, my mom’s first child is a girl’, however since I’m my mom’s first child it’s contingently false that my mom’s first child is a girl and contingently true that my mom’s first child is a boy… while ‘possibly, my mom’s first child is a girl (or boy)’ is still true.

Basically because I don’t hear atheists attacking the multiverse hypothesis with orbiting teapots or flying spaghetti monsters.