Possible worlds do not exist

[joppe]

I have heard an objection to the ontological argument.
It goes like this: "possible worlds do not exist".

I said to the atheist that "possible worlds are complete description of the actual world" and I was able to win the debate but how should I have dealt with it?

I showed many things that require possible worlds in order to conclude.
For example this:
"If A and B are different in some possible world, then A and B are not the same thing"

But how can I convince an atheist who says that possible worlds aren't there?
Should I use possible universes?

[Radian]

This was a problem for me as well. The only difference is that I was not entirely sure how to defend possible worlds outside of analogy with mathematics (sets for example).

[Asking_A_Question]

It might be because your language is ambiguous.  If you mean possible worlds exist as in every world that could be possible is actually a world, then this is known as modal realism and it has serious problems with it.  Nonetheless, that's not what Plantinga means when he uses the phrase.

If you mean possible worlds exist as in it is meaningful to talk about counterfactual states of affairs, then this is pretty solid.  This is the way Plantinga means possible worlds.  If anyone rejects this then they are implicitly saying that the sentence "you could have rolled a 4 instead of a six" is the same as "the blagnorg ate the flackshackeltez."  That seems highly unlikely.  Thus, you might want to simply choose better phrasing.

[veka]

If one believes that (physical) determinism is true, then they don't have doxastically possible world in which possible worlds (that is, counterfactual states of affairs) exists. So it depends on whether or not the atheist is committed to determinism.  If they are, it's not doxastically possible to them to believe in possible worlds.

[Biep]

A possible world is a maximal coherent description - that is, it either includes or excludes (contradicts with) any other description.  Possible worlds exist in the way the Pythagorean theorem exists.

And the number of physical determinists has declined dramatically since the discovery of quantum mechanics.  (Even though there are deterministic models of it, e.g. by Bohm.)
In fact, the standard "many worlds" interpretation attributes referential existence to many possible worlds (i.e. those worlds describe something that is actually "out there".)

[veka]

And the number of physical determinists has declined dramatically since the discovery of quantum mechanics.  (Even though there are deterministic models of it, e.g. by Bohm.)

Interesting. Doesn't physicalism entail physical determinism? Or am I wrong?

[veka]

Interesting. Doesn't physicalism entail physical determinism?

Well, maybe it doesn't.

[Biep]

There is agency determinism (there is another, more common name for this, which escapes me at the moment), which is about whether we could have chosen otherwise.  Being pushed one way by a deterministic process or by a truly random one doesn't make much of a difference in having taken agency (and responsibility) away from one.

Of course, under a many worlds interpretation, we did choose otherwise, but that world split off from the one we are pondering this in.  That is an interesting twist in agency determinism..

(And no, I don't think physicalism implies physical determinism.  It may hold that there is nothing beyond the - non-deterministic - physical world.)

[EDIT: The term is "agent causality".]

[veka]

(And no, I don't think physicalism implies physical determinism.  It may hold that there is nothing beyond the - non-deterministic - physical world.)

That was my afterthought exactly.

[campuspreacher]

The actual world is a possible world. Anything that is actually true is also possibly true so at least one possible world exists.

[SkepticAtheist]

I have heard an objection to the ontological argument.
It goes like this: "possible worlds do not exist".

I said to the atheist that "possible worlds are complete description of the actual world" and I was able to win the debate but how should I have dealt with it?

I showed many things that require possible worlds in order to conclude.
For example this:
"If A and B are different in some possible world, then A and B are not the same thing"

But how can I convince an atheist who says that possible worlds aren't there?
Should I use possible universes?

Most people who say possible worlds don't exist, don't understand the argument. What was his exact objection?

[joppe]

Most people who say possible worlds don't exist, don't understand the argument. What was his exact objection?

I don't remember that anymore

[Iapetus]

Reply to Joppe:

I said to the atheist that "possible worlds are complete description of the actual world" and I was able to win the debate.

An interesting conclusion on the basis of no evidence whatsoever but reliant purely on assertion.  In fact, I find it very difficult to even make sense of the clause, "possible worlds are complete description of the actual world”.  In what sense do possible worlds help to describe the actual world? Take, as an example, a description of our actual world as a place in which many people derive pleasure from dancing in response to a rhythmic pulse.  I could envisage a world in which green pixies with pitchforks force people to dance and prod them with a sharp stick if they don’t smile whilst doing so.  In what sense is that a “complete description of the actual world”?

I don’t even know if it is possible that green pixies with pitchforks could exist, since I am completely unable to define a scenario whereby I might examine the issue.  I certainly cannot prove that it is impossible, but neither does it follow that it is therefore possible.  I have no way of knowing and it cannot be assumed.

It is not sufficient to say that possible worlds may exist.  For your purposes you must demonstrate that they must exist.  I don’t see how you are going to do that.  Even working on the assumption of an infinite number of possible universes or outcomes, it does not follow that all possible outcomes must manifest themselves.  Some possibilities may repeat themselves, even an infinite numer of times.  Others may never ever appear.

[Vimbiso]

I have heard an objection to the ontological argument.
It goes like this: "possible worlds do not exist".

I said to the atheist that "possible worlds are complete description of the actual world" and I was able to win the debate but how should I have dealt with it?

I showed many things that require possible worlds in order to conclude.
For example this:
"If A and B are different in some possible world, then A and B are not the same thing"

But how can I convince an atheist who says that possible worlds aren't there?
Should I use possible universes?

@joppe the term possible worlds can be very confusing at times especially if people try to amalgamate its meaning with their own understanding of the word world. Simply put, a possible world is a conjunction of true propositions descriptive of the way the world could/can be. Defined that way, you can have numerous possible worlds e.g. there is a possible world in which I do not respond to your post. When I say there is a possible world in which X is true, I simply mean X is ontologically possible. The ontological argument's use of the term possible worlds is to simply assert that all different combinations of true propositions descriptive of the way the world could/can be, contain the proposition God exists. The assertion is that God is not only ontologically possible but also ontologically necessary.

Many people do not see possible worlds this way. To them there is only one world i.e. the actual world. However, to them the conjunction of true propositions descriptive of the way the actual world is contains contingent true propositions of the way the world could have been or can be. What the ontological argument calls possible worlds is what some antagonists call possible ways the world could have been or can be. They obviously deny the possible worlds terminology in order to refute the ontological argument but have only managed to make a semantic change without removing the real force behind the argument.

[Rob Heusdens]

I have heard an objection to the ontological argument.
It goes like this: "possible worlds do not exist".

I said to the atheist that "possible worlds are complete description of the actual world" and I was able to win the debate but how should I have dealt with it?

I showed many things that require possible worlds in order to conclude.
For example this:
"If A and B are different in some possible world, then A and B are not the same thing"

But how can I convince an atheist who says that possible worlds aren't there?
Should I use possible universes?

Use the multiverse, which is very likely given the amount of evidence for eternal inflating universe, but then the necessity of there being any god for creating the universe disappears with it....