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Possible Worlds, God exists.

TheMadFool October 31, 2021 at 04:09 9300 views 108 comments Philosophy of Religion
I was talking to @Bartricks in another thread about the notion of possibility. It led to something interesting.

If I say an argument is invalid it means there's a world in which all the premises are true and the conclusion is false.

If I now say, it's possible that God is (exists), by the same logic above, there is a world in which God really is (exists)

1. It is possible that God exists.

2. If something is possible then there is a world in which that something is real.

Ergo,

3. God exists.

QED

Comments (108)

khaled October 31, 2021 at 04:13 ¶ #614891
Not in this world necessarily though so who cares?
TheMadFool October 31, 2021 at 04:13 ¶ #614892
Quoting khaled
Not in this world necessarily though so who cares?


How do you know?
khaled October 31, 2021 at 04:14 ¶ #614893
Reply to TheMadFool your argument isn’t world specific. So you haven’t said anything about the existence of God in this world which is what people care about. That’s how I know that he doesn’t exist necessarily in this world, from your argument at least.

Also I disagree with premise 2.

Quoting TheMadFool
2. If something is possible then there is a world in which that something is real.


“Possible” means can exist in a possible world. Not actually exists in some world.
TheMadFool October 31, 2021 at 04:18 ¶ #614895
Quoting khaled
“Possible” means can exist in a possible world. Not actually exists in some world.


I disagree.

Quoting TheMadFool
If I say an argument is invalid it means there's a world in which all the premises are true and the conclusion is false.
Banno October 31, 2021 at 04:22 ¶ #614897
Quoting TheMadFool

1. It is possible that God exists.

2. If something is possible then there is a world in which that something is real.

Ergo,

3. God exists.


(1) reads "there is a possible world in which god exists"

SO yes, god exists in some possible world; but that possible world need not be the actual world.

The argument does not show that god exists in our world.

Moreover, god is usual take as necessarily existing - that it is not possible that god not exist; or that god exists in all possible worlds.

khaled October 31, 2021 at 04:23 ¶ #614898
Reply to TheMadFool You don’t need to agree with that one. The first critique doesn’t talk about any of the premises but the scope of the argument. The “God exists” that you came up with isn’t the “God exists” that people care about.
Deleted User October 31, 2021 at 04:27 ¶ #614902
This user has been deleted and all their posts removed.
Bartricks October 31, 2021 at 04:38 ¶ #614906
Reply to Banno Top marks for total inconsistency.

If Bartricks says it, it's false.

But elsewhere, Banno may say it and there it is true.

Are you being thick, or do you not care about consistency?

There's a possible world in which a contradiction is true. Doesn't mean any are true in the actual world, does it?
Banno October 31, 2021 at 04:52 ¶ #614910
Quoting Bartricks
There's a possible world in which a contradiction is true.


Possible worlds that include contradictions are called impossible worlds.

But what is really delightful is that you say both that you care about contradiction and that there are possible worlds with contradictions in them.
Jack Cummins October 31, 2021 at 05:04 ¶ #614914
Reply to TheMadFool
I don't see how that the idea of possibility in itself makes something 'real', because all it suggests is some remote chance rather than something definite. I am not sure how the concept of such a logical possibility would be of any use to anyone because those who adopt a belief in God are mainly interested in a being who they can relate to on a personal level rather than as a remote possibility.
TheMadFool October 31, 2021 at 05:27 ¶ #614916
Update

To all the above posters:

If a world x is possible but world x is not actual is acceptable then there's something not possible about an actual world.

1. World x is possible & World x is not actual (true according to all the posters above)

Ergo,

World x is actual can't be consistent with world x is possible. After all, world x is actual is the negation of world x is not actual.

A way out:

All possible worlds are actual worlds.
jorndoe October 31, 2021 at 05:42 ¶ #614919
Reply to TheMadFool, something's a bit off. By "the actual world" we normally just mean our world.

Quoting TheMadFool
All possible worlds are actual worlds.


With this (I think) you're moving towards modal realism, which means that all possible worlds are real, like our's is real.

A possible world need not be real, just possible, or let's say a self-consistent whole, if you will, even if hypothetical/imaginary/fictional.

TheMadFool October 31, 2021 at 05:50 ¶ #614920
Reply to jorndoe What's bothering me is the claim that the following statement is true:

1. X is a possible world & X is not an actual world.

If 1 is true then the following statement should be false:

2. X is a possible world & X is an actual world.

and even this should be false:

3. X is an impossible world & X is not an actual world.
Bartricks October 31, 2021 at 06:08 ¶ #614921
Reply to Banno Quoting Banno
Possible worlds that include contradictions are called impossible worlds.


Question begging. Nothing is impossible.
Anyway, call them what you like - I have no idea what a possible world is anyway - my point is that it is not necessarily true that there are no true contradictions, it is just true. Around and around we go.
jorndoe October 31, 2021 at 06:10 ¶ #614922
Reply to TheMadFool, instead of "an actual world", I'd use "the actual world", but maybe that's just me?

1. X is a possible world ? X is not the actual world = X is a possible world but not our's

Say, one where Napoleon drowned by suicide. At least that seems possible.

2. X is a possible world ? X is the actual world = X is our world

Or, instead of "an actual world", we could use "a real world", i.e. not fictional or merely imagined, despite being unknown to us.

1. X is a possible world ? X is not real = a possible world but imaginary/fictional

2. X is a possible world ? X is real = our world or another real world (unknown to us)

(Technically, there's a presumption that our world is a self-consistent whole, but that doesn't seem controversial; either way, the possible world semantics, I think, is intended to allow reasoning that includes our world, the actual world.)

If that makes any sense...

Banno October 31, 2021 at 06:14 ¶ #614924
Reply to jorndoe Yep.

@TheMadFool, the actual world is, after all, possible.
khaled October 31, 2021 at 06:54 ¶ #614928
Reply to TheMadFool Quoting TheMadFool
1. World x is possible & World x is not actual (true according to all the posters above)


I don't think anyone said this. What was said was: If world X is possible, that doesn't imply it's actual.

Quoting TheMadFool
Ergo,

World x is actual can't be consistent with world x is possible. After all, world x is actual is the negation of world x is not actual.


But this doesn't follow from either "world X is possible and not actual" or "If world X is possible, that doesn't imply it's actual"
180 Proof October 31, 2021 at 07:03 ¶ #614930
Quoting jorndoe
A possible world need not be real, just possible, or let's say a self-consistent whole, if you will, even if hypothetical/imaginary/fictional.

:up:

Reply to TheMadFool "God" is undefined, therefore the argument is invalid.
I like sushi October 31, 2021 at 07:09 ¶ #614932
Reply to TheMadFool Again, this depends on what is meant by 'God'. Define it and it is possible. Don't define it and it is meaningless.

It really is that simply (or complex).
I like sushi October 31, 2021 at 07:11 ¶ #614934
I do actually have a definition of god though. I think most other people would call it 'me' though and dismiss themselves as ever inhabiting even an iota of godhood.

I'm not happy to say I am god but I am aware of its truth nevertheless.
TheMadFool October 31, 2021 at 07:34 ¶ #614937
To all

Suppose X is a possible world and is not actual.

Ergo, the following statement is true.

1. X is possible & X is not actual

If so, the statement

2. X is possible & X is actual

has to be false because X is not actual (X is actual is false)

But then look at 2. It says something odd: X is possible and actual is false.
DecheleSchilder October 31, 2021 at 07:46 ¶ #614940
Quoting TheMadFool
If I say an argument is invalid it means there's a world in which all the premises are true and the conclusion is false.


Already here you make a mistake. There exists a logic for which this doesn't necessarily hold. Even necessity looses it's usual meaning in this logic.
khaled October 31, 2021 at 08:19 ¶ #614944
Reply to TheMadFool Quoting TheMadFool
Suppose X is a possible world and is not actual.

Ergo, the following statement is true.

1. X is possible & X is not actual

If so, the statement

2. X is possible & X is actual

has to be false because X is not actual (X is actual is false)

But then look at 2. It says something odd: X is possible and actual is false.


Obviously it says that because we established from the first line that X is possible and not actual. If we are talking about this world, well it's possible and actual.

The only way I can imagine you thinking this is odd is if you generalize X. As in, given a world, X, the above follows. But it doesn't follow, because if you generalize X you can't say that X is possible and not actual.
TheMadFool October 31, 2021 at 08:43 ¶ #614953
Quoting jorndoe
instead of "an actual world", I'd use "the actual world", but maybe that's just me?

1. X is a possible world ? X is not the actual world = X is a possible world but not our's

Say, one where Napoleon drowned by suicide. At least that seems possible.

2. X is a possible world ? X is the actual world = X is our world

Or, instead of "an actual world", we could use "a real world", i.e. not fictional or merely imagined, despite being unknown to us.

1. X is a possible world ? X is not real = a possible world but imaginary/fictional

2. X is a possible world ? X is real = our world or another real world (unknown to us)

(Technically, there's a presumption that our world is a self-consistent whole, but that doesn't seem controversial; either way, the possible world semantics, I think, is intended to allow reasoning that includes our world, the actual world.)

If that makes any sense...


:ok:

I'm mainly interested in what follows from the claim that a possible world need not be actual.

Suppose X is a possible world and that's all we know.

Then the following is true:

1. X is possible & X is not actual.

I'm working with my intuition here so bear with me.

I conclude from 1 that there's something not actual about possible. In other words, there's a gap between the possible and the actual.

How come then that when the poles are reversed, there's a connectionn the gap I mentioned above is bridged, as in if X is actual then X is possible

Summary:

1. If X is possible then X is actual (False i.e. there's a gap between possible and actual)

2. If X is actual then X is possible (True? What happened to the gap mentioned above?)
khaled October 31, 2021 at 09:19 ¶ #614966
Reply to TheMadFool Quoting TheMadFool
a possible world need not be actual.


So P does not lead to A.

Quoting TheMadFool
Suppose X is a possible world and that's all we know.


X is P

Quoting TheMadFool
1. X is possible & X is not actual.


Thus X is P and !A? That doesn't follow. I think you're confusing "P does not lead to A" with "P leads to !A". With the latter it makes sense, but no one claimed that.

Quoting TheMadFool
1. If X is possible then X is actual (False i.e. there's a gap between possible and actual)

2. If X is actual then X is possible (True? What happened to the gap mentioned above?)


These "gaps" are sometimes not two way.

For example "If X is a butler, X is human", True. "If X is human, X is a butler", False. See?

Because the set of all butlers is a subset of the set of all humans. Similarly, the set of actual worlds, is a subset of the set of possible worlds.
TheMadFool October 31, 2021 at 09:20 ¶ #614967
@Banno, @Bartricks, @180 Proof, @I like sushi@DecheleSchilder, @khaled, @jorndoe@Jack Cummins, @tim wood

Possible

1. If X is possible then not necessary that X is actual.

Ergo,

2. There's a gap between possible and actual.

Actual

3. If X is actual then necessary that X is possible.

Ergo,

4. There's no gap between possible and actual

5. There's a gap between possible and actual & There's no gap between possible and actual. [Contradiction!]

khaled October 31, 2021 at 09:21 ¶ #614969
Reply to TheMadFool "There is a gap" is not a logical statement. I think what you mean to say is: Possible does not imply Actual. And 3 shows that Actual does imply Possible. Nothing wrong with that.

Quoting khaled
These "gaps" are sometimes not two way.

For example "If X is a butler, X is human", True. "If X is human, X is a butler", False. See?

Because the set of all butlers is a subset of the set of all humans. Similarly, the set of actual worlds, is a subset of the set of possible worlds.


TheMadFool October 31, 2021 at 09:23 ¶ #614970
Quoting khaled
There is a gap" is not a logical statement.


How can you say that? What's not logical about it?

Why do you say that it's "...not two way"? If there's a gap between point A and point B, it doesn't matter whether I'm at point A or B, there's a gap.
khaled October 31, 2021 at 09:24 ¶ #614971
Reply to TheMadFool Quoting TheMadFool
If there's a gap between point A and point B, it doesn't matter whether I'm at point A or B, there's a gap.


But we're not talking about points in space are we?
TheMadFool October 31, 2021 at 09:24 ¶ #614973
Quoting khaled
But we're not talking about points in space are we?


Of course, it's an analogy. You got it, right?
khaled October 31, 2021 at 09:26 ¶ #614974
Reply to TheMadFool But it's not analogous at all.

In logic, A can imply B without B implying A right? Now replace "A" with "Actual" and "B" with "Possible"

Conversely, that B does not imply A doesn't mean A does not imply B. That's why a "gap" is not analogous. Because it's possible to be able to move from A to B without it being possible to move from B to A.
DecheleSchilder October 31, 2021 at 10:30 ¶ #614983
Reply to TheMadFool

There is a gap in mutual understanding here. All gaps can be logical, while at the same time being being realty-detached. Which logic is. A gap can exists litterally in spacetime, as a hole in a black.Though a gap in the common physicists mind is due to this gap. There can be gaps between all possible worlds of knowledge, as is surely the case in this case. There simply is no universal gap, and to pretend there is to deny the gaps of fellow people turning the discussion into a battle between the gaps.Which is very interesting, articulating the various gaps we have as human beings. The articulation of the gap seems, in my humble mind, a nice philosophical discussion, savely remote from standard lexicon like that standard dictionaries of Stanford and related institutions. Ah yes, the gap. How many of them I still have jump over, before reaching Nirvana? How many bridges I try to build, they always seem to crumble right after. Poor me. Luckily I have the power of the word, imagination, and sense of relativity, a God-given present, which came packed inside the God-given gift of life and existence. I rejoyce in the mad fool having found a logical proof of the obvious! Though I'm not sure what Quantum ElectroDynamics have to do with it.
180 Proof October 31, 2021 at 10:59 ¶ #614986
Reply to TheMadFool :meh:
Quoting 180 Proof
Metaphysics ... proposes criteria for discerning 'impossible worlds' (i.e. ways actuality necessarily cannot be) from 'possible worlds' (i.e. ways actuality can be) – btw, I'm an actualist, not a possibilist – thereby concerning the most general states of affairs ...

such that
Quoting 180 Proof
... by "a possible world" I understand a possible version of actuality (i.e. a possible way the actual world could have been or can be described), such that "actual" is not an index for any "possible world" at issue but rather is the extant domain, or universe, of possibilities (à la phase-space).

and so a purported "gap between possible and actual" is conceptually incoherent in actualist terms. You're only chasing "possibilist" shadows, Fool, deeper and deeper into Meinong's Jungle. :chin:
theRiddler October 31, 2021 at 11:07 ¶ #614988
I don't think there is a gap. If X is possible, X is actual. There's no such thing as a possible thing that isn't actual, except in colloquial terms.

I'm not sure if there's a philosophy centered around what philosophers mean when they say "possible." One only needs to know that God is possible to prove God exists, IMO.

The only things that can't possibly be known to be false are truths, as it's possible God exists and knows all things, true and false, and God can't possibly know Itself to be false.
theRiddler October 31, 2021 at 11:08 ¶ #614989
lol It's so confusing. I'm out! Time to put this idiot to bed.
theRiddler October 31, 2021 at 11:14 ¶ #614992
I am a theist, I believe in Holiness anyway...but how does God ever know that it wasn't created by the real God to believe it is God? And how does the real God know that, etc.
180 Proof October 31, 2021 at 11:44 ¶ #614998
Reply to theRiddler :eyes:
Theism is not true, "God" is imaginary; therefore your problem is (dis)solved. And if you're a theistic anti-realist (i.e. theological noncognitivist), then "the real God" makes no more sense than "the real Middle Earth".
theRiddler October 31, 2021 at 11:53 ¶ #614999
Reply to 180 Proof

Lots of imaginary things are true. Unicorns, for example.
180 Proof October 31, 2021 at 12:00 ¶ #615003
Quoting theRiddler
Lots of imaginary things are true. Unicorns, for example.

Statements, not objects, can be true. :roll:
theRiddler October 31, 2021 at 12:05 ¶ #615006
Shoulda figured you'd call me on that, but I disagree anyway.

There are more things in Heaven and Earth, Horatio.
khaled October 31, 2021 at 12:09 ¶ #615008
Reply to theRiddler Quoting theRiddler
I don't think there is a gap. If X is possible, X is actual.


The God that kills the Christian God possibly exists, his name is Will Hoff.
Therefore Will Hoff exists.
God is dead and Will Hoff killed him.

It is also possible that you're not Christian and are actually lying about being Christian. Therefore it is actually the case that you're not Christian and are actually lying about being Christian.

You could be wrong about the possible being actual. Therefore you're wrong about the possible being actual. You could also be right about the possible being actual. Therefore you're right about the possible being actual. So you're right and wrong about the possible being actual.

And a whole lot of other messes happen when what's possible is what's actual.
theRiddler October 31, 2021 at 12:38 ¶ #615021
Uh...I don't care what you name God...

I couldn't possibly be wrong if I'm right. I'm gonna go now and let you atheists try to solve the mystery of your anal retention.
DecheleSchilder October 31, 2021 at 13:18 ¶ #615030
Quoting theRiddler
I ouldn't possibly be wrong if I'm right. I'm gonna go now and let you atheists try to solve the mystery of your anal retention.


Great comment! I am sure there are gods. No one can prove me wrong how well they try scientifically (on which grounds I usually am the better).
khaled October 31, 2021 at 13:21 ¶ #615032
Reply to theRiddler Quoting theRiddler
I couldn't possibly be wrong if I'm right.


But also, it's possible for you to be wrong, but only think you're right. And since if something is possible it is factual, you are in fact wrong.

It is also possible for you to be right while thinking you're right. So you are indeed right.

You're right and wrong.
TheMadFool October 31, 2021 at 13:24 ¶ #615034
To All

First things first, what we agree on.

1. If X is an actual world then X is a possible world.

Now, the sticking point,

2. If X is a possible world then X is an actual world.

Statement 2, all of you say is false.

Consider now the following statement (contrapositive of 2)

3. If X is not an actual world then X is not a possible world (contrapositive of 2)

Invoking the principle of sufficient reason, if X is not an actual world, it follows that there are reasons why X is not an actual world. These reasons show why X can't be an actual world. In other words, there's an argument that proves X is not a possible world.

That is to say, it's true that,

3. If X is not an actual world then X is not a possible world.

Undoing what we did, we get

4. If X is a possible world then X is an actual world (contrapositive of 3). This statement is true.

QED.
Deleted User October 31, 2021 at 14:46 ¶ #615068
This user has been deleted and all their posts removed.
ninjachewit October 31, 2021 at 14:53 ¶ #615070
Possible worlds are only relevant when it comes to propositions. The possible worlds make up for the sense ingredient for each separate reference. It does not point at the truth at all. For example, there is a world where snow is blue but in this world snow is white, so we get a sense of "white" when we mention snow because in this world snow is white.

Therefore possible worlds are needed as a way for us to make sense of what is NOT. It has no value when it comes to proving something that may exist in our world.
Deleted User October 31, 2021 at 14:56 ¶ #615071
This user has been deleted and all their posts removed.
ninjachewit October 31, 2021 at 15:07 ¶ #615077
Reply to TheMadFool Also this is what you're saying.

1. If X is an actual world then X is a possible world.
2. If X is a possible world then X is an actual world.

I can also say:

1. If is apple then it is a fruit
2. If is fruit then it is an apple

Possible world has a greater scope that contains all actual worlds
Therefore you can't say that a possible world is an actual world because possible worlds do not completely contain actual worlds in its set- there are some worlds that are just potential. Otherwise it would be not be a set of potential worlds but actual worlds.
Manuel October 31, 2021 at 16:26 ¶ #615096
Reply to TheMadFool

In a possible world we could be ants in the playground of a little kid. In another possible world there is a massive horse that rules the universe.

Therefore being ants in a playground and being subject to the whims of a horse are real. But if these words have no causal influence on ours at all, does it matter?

In other words, if God exists in another possible world what meaningful difference does that entail for us here? I can think of nothing, but perhaps you can tell me what I currently not seeing.
TheMadFool October 31, 2021 at 16:48 ¶ #615099
Quoting tim wood
"Is not," "can't be": not interchangeable, not substitutable one for the other. Yours, then QE~D.


Suppose a world Y is not actual. Why? There has to be a reason why that is. That reason becomes an argument the conclusion of which is Y is not actual. A conclusion is necessarily true i.e. Y is not actual implies Y is necessarily not actual. If Y is necessarily not actual then Y is not possible. Therefore, Y is not actual implies Y is not possible. That means Y is possible entails Y is actual. QED.



TheMadFool October 31, 2021 at 16:54 ¶ #615102
Quoting ninjachewit
Also this is what you're saying.

1. If X is an actual world then X is a possible world.
2. If X is a possible world then X is an actual world.

I can also say:

1. If is apple then it is a fruit
2. If is fruit then it is an apple

Possible world has a greater scope that contains all actual worlds
Therefore you can't say that a possible world is an actual world because possible worlds do not completely contain actual worlds in its set- there are some worlds that are just potential. Otherwise it would be not be a set of potential worlds but actual worlds.


Read my reply to tim wood

I'll repeat myself at the risk of boring you but it's quite exciting to say the least.

If a possible world X is not actual, there's got to be a reason why. That reason, in an argument, proves X is not actual. In an argument, the conclusion (here X is not actual) is necessarily true.

Therefore,

1. X is not actual implies X is necessarily not actual.

2. X is necessarily not actual implies X is not possible.

3. X is not actual implies X is not possible (1, 2 HS)

Ergo,

4. X is possible implies X is actual (3 Contra)

QED

Deleted User October 31, 2021 at 18:37 ¶ #615126
This user has been deleted and all their posts removed.
TheMadFool October 31, 2021 at 20:25 ¶ #615175
Quoting tim wood
This: =>, is not the same as this <=>. Implies does not mean means.
And you still have the problem of validity, truth/falsity, soundness. And even this not a complete specification.

George is at home or George is at the store.
George is not at home.
George is at the store.

Valid, true, sound. But oops, George isn't at the store! Logic, caveat emptor. Or at least understand its limits and boundaries.


I have no idea what you're trying to say here.

My argument is rather simple.

Suppose X is not an actual world.

There has to be an reason why it's not actual (the principle of sufficient reason).

What does having a reason for X is not actual mean?

It simply means that we have an argument that proves X is not actual. If there's a proof for X is not actual, it implies X is necessarily not actual.

In other words,

1. If X is not actual then X is necessarily not actual.

2. If X is necessarily not actual then X is not possible.

Ergo,

3. If X is not actual then X is not possible (1, 2 HS)

Ergo,

4. If X is possible then X is actual (3 Contra)

QED
Banno October 31, 2021 at 20:32 ¶ #615178
Quoting TheMadFool
Suppose a world Y is not actual. Why? There has to be a reason why that is.

There is a possible world in which my cat is ginger.

In the actual world, he is black.

Now the reason, if you need one, that the possible world in which my cat is ginger is not the actual world is that my cat is black.

TheMadFool October 31, 2021 at 20:34 ¶ #615180
Update

World X is not actual.

Why?

Reason R

Argument A1:

1. R

Therefore,

2. World X is not actual

However, given argument A1,

3. Necessary that world X is not actual.

4. If world X is not actual then necessary that world X is not actual. [from 2, 3]

Argument A2:

5. If necessary that world X is not actual then world X is impossible.

Argument A3:

6. If world X is not actual then world X is impossible [4, 5 HS]

Ergo,

7. If world X is possible then world X is actual [6 Contra]

QED.
Banno October 31, 2021 at 20:39 ¶ #615184
Quoting TheMadFool
1. If X is not actual then X is necessarily not actual.


Nuh. "Actual" is an indexical. Like left and right. The folk in each possible world think they are in the actual world.

Add that "Necessarily" is just "In all possible worlds", and hopefully you will see why your proposition is ill-formed.

Janus October 31, 2021 at 20:48 ¶ #615187
Reply to TheMadFool The problem with this argument is that the idea of God is not that he could exist in some possible world, but that insofar as he could be said to exist in any world then he necessarily exists in every possible world. But that, being a mere idea, doesn't tell us anything about God actually existing. This argument fails in the same way as the Ontological Argument.
Varde October 31, 2021 at 20:52 ¶ #615191
I don't think all possible worlds exist(perhaps in a paradox).

There is randomness, not only technicality; not every world ends up being made depending on supply and demand.

The thought of possible worlds is the thought of a paradox, an illusionary phenomenon.

Are there any actual worlds where God exists?

Though, I may be wrong, there may be a creative entity that creates all possible worlds [I]for the hell of it[/I].



Janus October 31, 2021 at 20:52 ¶ #615192
Quoting Banno
There is a possible world in which my cat is ginger.

In the actual world, he is black.


That whole idea is incoherent. Your cat could not be ginger in any possible world, because it would not be the same cat. All you're saying is that there could be a ginger cat in some possible world, which is trivially true. Modal logic is garbage.
TheMadFool October 31, 2021 at 20:54 ¶ #615194
Quoting Banno
Suppose a world Y is not actual. Why? There has to be a reason why that is.
— TheMadFool
There is a possible world in which my cat is ginger.

In the actual world, he is black.

Now the reason, if you need one, that the possible world in which my cat is ginger is not the actual world is that my cat is black.


Let me get this straight.

1. Your cat (in the actual world) is black

Therefore,

2. The possible world in which your cat is ginger is not the actual world.

The word "the" is key. Of course any possible world which differs from this (the) actual world is not this world. However that doesn't prove that those possible worlds are not actual. You're assuming that this (the) world is the only actual world.

Quoting Banno
Nuh. "Actual" is an indexical. Like left and right. The folk in each possible world think they are in the actual world.

Add that "Necessarily" is just "In all possible worlds", and hopefully you will see why your proposition is ill-formed.


The word "actual" as an indexical is not, I think, important. My argument has little to do with modal realism although we come to the same conclusion.
Banno October 31, 2021 at 20:55 ¶ #615197
Quoting Janus
Your cat could not be ginger in any possible world, because it would not be the same cat.

Nuh. Jack - a rigid designator - might have been ginger. That sentence makes sense. It's exactly the sort of thing modal logic is intended to deal with.

Jack's identity is maintained across possible worlds.

Banno October 31, 2021 at 20:58 ¶ #615200
Quoting TheMadFool
You're assuming that this (the) world is the only actual world.


Actually I explicitly said that the folk in each possible world think their world is the actual world.

But yes, there is only one actual world, within the structure of modal logic.

Quoting TheMadFool
The word "actual" as an indexical is not, I think, important.


If you think that, you've missed the point.
Banno October 31, 2021 at 21:02 ¶ #615203
What's odd is that possible worlds should cause such confusion. The capacity for folk to miscomprehend is astonishing.

A new universe did not pop into existence when I pointed out that Jack might have been ginger*. It's just a way of talking about such possibilities that clarifies the relations of possibility and necessity. Mad, you are over-egging the ontology.


(*that sort of rubbish is the domain of quantum.)
ninjachewit October 31, 2021 at 21:09 ¶ #615208
Reply to TheMadFool

Your reasoning still lies in the fallacy that I discovered.

This is what you say:

1. If X is an actual world then X is a possible world.

2. If X is a possible world then X is an actual world.

Consider now the following statement (contrapositive of 2)

3. If X is not an actual world then X is not a possible world (contrapositive of 2)

3. If X is not an actual world then X is not a possible world.

Undoing what we did, we get

4. If X is a possible world then X is an actual world (contrapositive of 3). This statement is true.

If X is an actual world (if apple is a fruit) then it is a possible world (a possible fruit) See how this argument is beginning to fall apart? You're stating that something real is a possibility of being real. This is a logical contradiction. Moving on.

If X is a possible world (a possible fruit) then X is an actual world (an actual fruit)

Still this doesn't make sense because as I said, the set of all possible conditions must be greater than the set of all actual objects. This is because a set of possible X should mean there is number of X that is not actual. The set of possible worlds therefore is greater than the set of actual worlds.

Therefore, we cannot say your second point as it is a logical contradiction. If X is a possible world it does not mean that X is an actual world because the set of X as possible worlds is bigger than the latter. Moving on.

You say in point 3 that if X is not an actual world then X is not a possible world. This contradictions everything you've said and been building up to so far. I can imagine a world that is made of gas, and although this planet is not real, it can be a possible world because it contains all the conditions of being real. For example, if something has possible properties then it is possible but not always actual.

Going to point 4 now which is built upon several logical mishaps, we will see that the conclusion must be false or at least doubtable. This can be done simply however.

Fourth point: If X is a possible world then X is an actual world. You just said in point 3 that if X is not an actual world then X is not a possible world. This is a complete contradiction to each other.

According to what you said, the set containing all possible worlds is equivalent to the set of all actual worlds. First of all "possible" means that there is a possibility that the world in question is not actual. This means that the set of possible worlds can never equal the set of actual worlds, because actual worlds are manifestations of conditions whereas possibility itself is a condition to be questioned. Therefore possibility is always superior in its set than actual manifestations of it, otherwise there is no need to use the word "possibility"- merely just call it actual- but before actuality there is always possibility and therefore the two cannot be equated to each other as you have done.

TheMadFool October 31, 2021 at 21:09 ¶ #615209
Quoting Banno
Actually I explicitly said that the folk in each possible world think their world is the actual world.

But yes, there is only one actual world, within the structure of modal logic.


I don't buy that. How can modal logic (about possibilities and necessities) ever even claim there is only one actual world.

Quoting Banno
If you think that, you've missed the point.


I believe you're barking up the wrong tree here.

Let's try another route.

1. World X is possible & World X is not actual (you would agree)

2. World X is impossible & World X is not actual (obvious)

I give you world Z which is not actual. That is to say,

3. World Z is not actual.

Question for you: Is world Z impossible or is world Z possible?

How would you be able to tell?
Banno October 31, 2021 at 21:17 ¶ #615218
Quoting TheMadFool
How can modal logic (about possibilities and necessities) ever even claim there is only one actual world.


It doesn't. Rather, the folk in each world think their worlds is the actual world. Third time I've said it.

Quoting TheMadFool
Question for you: Is world Z impossible or is world Z possible?


Might be either. You haven't yet specified.

Quoting TheMadFool
How would you be able to tell?


When I said Jack might have been a ginger, I specified the nature of a possible world - one in which Jack was a ginger. SO, go ahead and decide if Z is possible or impossible by specifying what's special about it.

Banno October 31, 2021 at 21:20 ¶ #615222
Quoting Banno
It doesn't. Rather, the folk in each world think their worlds is the actual world. Third time I've said it.


I suppose we might specify a possible world such that the folk therein believe their world is not the actual world.

A world of mad fools?
TheMadFool October 31, 2021 at 21:20 ¶ #615223
Quoting Banno
Might be either. You haven't yet specified.


You had to come up with the solution.

Banno October 31, 2021 at 21:21 ¶ #615224
Quoting TheMadFool
You had to come up with the solution.


It's what I do.
Janus October 31, 2021 at 21:21 ¶ #615225
Quoting Banno
Nuh. Jack - a rigid designator - might have been ginger. That sentence makes sense. It's exactly the sort of thing modal logic is intended to deal with.

Jack's identity is maintained across possible worlds.


It's nothing but a fantasy. If it gives you pleasure to imagine you are thinking something coherent when you say that your cat could have been different than he is,. I suppose there's little harm in it.
TheMadFool October 31, 2021 at 21:21 ¶ #615226
Quoting Banno
I suppose we might specify a possible world such that the folk therein believe their world is not the actual world.

A world of mad fools?


:chin:
TheMadFool October 31, 2021 at 21:21 ¶ #615228
Quoting Banno
It's what I do.


So? Where's your solution?
Banno October 31, 2021 at 21:21 ¶ #615229
Reply to TheMadFool Don't... I shouldn't have...

Stop while you are ahead.
Banno October 31, 2021 at 21:22 ¶ #615232
Quoting TheMadFool
Where's your solution?


What's the problem?
180 Proof October 31, 2021 at 21:23 ¶ #615236
@TheMadFoolQuoting Janus
?TheMadFool The problem with this argument is that the idea of God is not that he could exist in some possible world, but that insofar he could be said to exist in any world then he necessarily exists in every possible world. But that, being a mere idea, doesn't tell us anything about God actually existing. This argument fails in the same way as the Ontological Argument.

:up:
Banno October 31, 2021 at 21:23 ¶ #615237
Quoting Janus
It's nothing but a fantasy.


One I share with most modal logicians and others since Kripke.

But I think we've had this conversation before? Have you forgotten, again?
TheMadFool October 31, 2021 at 21:24 ¶ #615238
Quoting Banno
What's the problem?


Quoting TheMadFool
1. World X is possible & World X is not actual (you would agree)

2. World X is impossible & World X is not actual (obvious)

I give you world Z which is not actual. That is to say,

3. World Z is not actual.

Question for you: Is world Z impossible or is world Z possible?

How would you be able to tell?


TheMadFool October 31, 2021 at 21:25 ¶ #615239
Banno October 31, 2021 at 21:25 ¶ #615240
Quoting TheMadFool
Is world Z impossible or is world Z possible?


Quoting Banno
Might be either. You haven't yet specified.


Varde October 31, 2021 at 21:25 ¶ #615241
What you suggest is that there is an atomic world where each configuration of a grain of sand in every possible desert is actualised in possible worlds. Clearly not mate. On the other hand there could be a paradox of all these worlds, in a holographic light. Even then, it seems a bit too stark. I would suggest thinking any world is possible, but only those we demand are made.
Banno October 31, 2021 at 21:27 ¶ #615244
Quoting Varde
What you suggest is that there is an atomic world where each configuration of a grain of sand in every possible desert is actualised in possible worlds. Clearly not mate.


Who you talking too?

Either click on the back arrow at the bottom of a post to reply, or highlight a piece of text in a pst and click on "quote".

Or if all else fails, use a name instead of "You"
Varde October 31, 2021 at 21:28 ¶ #615245
Reply to Banno theMadFool.

Okay I will do that from now on.
Banno October 31, 2021 at 21:28 ¶ #615246
Reply to Varde Cheers.
Janus October 31, 2021 at 21:31 ¶ #615249
Reply to Banno My memory tells me we probably have had a conversation, not identical, but roughly along similar lines as this one before.
TheMadFool October 31, 2021 at 21:37 ¶ #615254
Banno October 31, 2021 at 21:44 ¶ #615261
Reply to TheMadFool
You seem to think of possible worlds as things we find and investigate, through a microscope or telescope.

They are just stuff we make up. A way of talking about possibilities.

SO, when you tell us more about world Z, we might decide if it is possible or not.
TheMadFool October 31, 2021 at 21:45 ¶ #615262
Update

1. If world X is not actual then there's a proof why world X is not actual.

2. If there's a proof that world X is not actual then necessarily world X is not actual.

3. If necessarily world X is not actual then world X is impossible.

4. If world X is not actual then necessarily world X is not actual. (1, 2 HS)

5. If world X is not actual then world X is impossible. (3, 4 HS)

6. If world X is possible then world X is actual. (5 Contra)
TheMadFool October 31, 2021 at 21:45 ¶ #615263
Reply to Banno Can you have a look [math] \uparrow [/math].
Banno October 31, 2021 at 22:00 ¶ #615277
Quoting TheMadFool
1. If world X is not actual then there's a proof why world X is not actual.

Nuh. The "proof" is just you specifying that X is the actual world or that it isn't.

Quoting TheMadFool
2. If there's a proof that world X is not actual then necessarily world X is not actual.

Nuh. The "proof" is just you specifying that X is not the actual world or that it is. But also, the phrase "Necessarily word X is not actual" is ill-formed. It comes out as something like "in all possible worlds world X is not actual"; which presumably is just "World X is impossible".

Try substituting "in all possible worlds" for "necessarily" in your thinking; you may begin to see why the possible world way of talking clears the air. The confusion you are suffering might be because you are mixing two ways of speaking about modality.



Banno October 31, 2021 at 22:18 ¶ #615292
Reply to Janus Yeah. It just seems to me you haven't grasped the purpose of rigid designators.
Janus October 31, 2021 at 22:32 ¶ #615301
Reply to Banno I understand that you can stipulate that, on account of having been named, an entity can be imagined to have been different than they are in actuality. So I could be imagined to have been born a woman, for example. And according to the idea that my identity is established by naming (rigid designation) my identity is thereby hermetically sealed from alteration despite any and all conceivable alternate forms I can be imagined to have taken in other possible worlds.

But the limits to this cannot be coherently established. It might seem coherent to say I could have been born a woman, but what about the idea that I could have been a stone, a tree or a mountain? I think the inconceivability of this (absent the idea of a unique individual soul or essence or something like that) shows that description plays an ineliminable part in establishing identity, if not in merely stipulating it..
Banno October 31, 2021 at 22:39 ¶ #615306
Reply to Janus That just looks like a misconstrual of the way rigid designation works.

What if Janus had a haircut yesterday? What if Janus had never developed an interest in modality? What if Janus had been born a woman? What if Janus were a rock? What if Janus were not identical with Janus?

Some of these are possible worlds, some impossible worlds, and for different reasons. The semantics helps us sort them out.
Janus October 31, 2021 at 23:01 ¶ #615318
Quoting Banno
What if Janus had a haircut yesterday? What if Janus had never developed an interest in modality? What if Janus had been born a woman? What if Janus were a rock? What if Janus were not identical with Janus?

Some of these are possible worlds, some impossible worlds, and for different reasons. The semantics helps us sort them out.


Sure we can try to imagine all those things and discover the special conditions we would need to posit to make them coherently imaginable (as opposed to merely saying them). But such things were done long before rigid designation ever became an explicit thing. Think about aboriginal myths, for example.
Banno October 31, 2021 at 23:22 ¶ #615330
Reply to Janus Sure.

Rigid designation is just a new term for something we've done all along. It serves to set out what we are doing, and to allow is to differentiate between certain modal problems in a way that allows us to dissipate or explain them.

Janus October 31, 2021 at 23:25 ¶ #615331
Reply to Banno That's true; and I have to agree it is helpful to make explicit to ourselves what we are doing. Perhaps I have been looking for more in the ideas of rigid designation and possible worlds than I should have.
Banno October 31, 2021 at 23:28 ¶ #615334
Reply to Janus Cheers. To be sure, there are folk who do think along those lines. But I think treating modality as mooted daydreams avoids most, if not all, of the various pitfalls ascribed to possible world semantics.
Janus October 31, 2021 at 23:32 ¶ #615337
Reply to Banno OK thanks, that's been helpful; you've altered my perspective re modal logic. :smile:
Banno October 31, 2021 at 23:34 ¶ #615338
Deleted User October 31, 2021 at 23:40 ¶ #615340
This user has been deleted and all their posts removed.
180 Proof October 31, 2021 at 23:42 ¶ #615342
Quoting tim wood
Please give predicates for "actual," "possible," "necessary." No predicates, no precision; no precision, no proof.

:up:
khaled November 01, 2021 at 08:45 ¶ #615482
Reply to TheMadFool Quoting TheMadFool
1. If world X is not actual then there's a proof why world X is not actual.


Not necessarily. There could be some true statements we can't prove (incompleteness)

Quoting TheMadFool
2. If there's a proof that world X is not actual then necessarily world X is not actual.


Wot? Max I'd be willing to say is "If there is valid proof that world X is not actual then we are justified in believing that world X is not actual"

Quoting TheMadFool
4. If world X is not actual then necessarily world X is not actual. (1, 2 HS)


But those premises are false.
TheMadFool November 01, 2021 at 11:12 ¶ #615516
Quoting tim wood
given 1) ~w
given 2) ?(~w) ?(r): r => ~w
assume r, therefore ~w
Not a giant step for logic.

Please give predicates for "actual," "possible," "necessary." No predicates, no precision; no precision, no proof


Why? Sentential logic works fine.

Quoting khaled
Not necessarily. There could be some true statements we can't prove (incompleteness)


You're bending over backwards, going to great lengths as it were, to make a point. You have to prove incompleteness whatever that means in your case.

Here's the deal. I present to you a world Z that is not actual.

The question: Why is world Z not actual?
khaled November 01, 2021 at 12:11 ¶ #615527
Reply to TheMadFool Quoting TheMadFool
You have to prove incompleteness whatever that means in your case.


No I don't. You stated the premise that if something is true, we can prove it. Prove that premise. You think if it is true, there should be a proof for it, so where is the proof for that.

I don't need to definitively state or even prove that there are true, unprovable statements. Because I'm not making a case here. You have a dubious premise in your argument, you need to back it up. It is not at all obvious that every true statement has a proof, not since Godel.

Quoting TheMadFool
Here's the deal. I present to you a world Z that is not actual.

The question: Why is world Z not actual?


Here is the deal. I present to you a red car.

The question: Why is this car red?

Answer that and I'll tell you why Z is not actual.
TheMadFool November 01, 2021 at 12:50 ¶ #615535
Quoting khaled
Here is the deal. I present to you a red car.

The question: Why is this car red?

Answer that and I'll tell you why Z is not actual.


:lol: I have not time for your silly games khaled
Deleted User November 01, 2021 at 13:45 ¶ #615541
This user has been deleted and all their posts removed.
Varde November 01, 2021 at 14:07 ¶ #615547
Doesn't it equalise itself, God does and doesn't exist? Do you see the paradoxical effect?

The only worlds where God actually exists are not equalised by an amount of worlds where God doesn't.

So how does God exist, if equally he doesn't?
SpaceDweller November 01, 2021 at 14:39 ¶ #615549
Reply to Varde
How is that paradox if there is no certainty nor self-contradiction?