What does it mean for something to be "logically possible"?

[Bomb#20]

Logic doesn't make things possible; illogic makes things impossible. For something to be logically possible there are two requirements. It must not involve a contradiction in terms, and the criteria for it must be clear.

So, that said, no, it isn't logically possible that Jesus was the son of god or that the Big Bang was a miracle of some bored gods, because the words "god" and "miracle" have no clear meaning.
...

I don't think clarity is a necessary condition for whether some proposition is logically possible. Knowledge of whether some proposition is logically possible (maybe), but that's a tad bit different.

Clarity is really a property of sentences, not propositions. If a sentence is unclear then it doesn't stand for any particular proposition, so it doesn't make a lot of sense to say the proposition it stands for is logically possible.

 

[untermensche]

I don't think clarity is a necessary condition for whether some proposition is logically possible. Knowledge of whether some proposition is logically possible (maybe), but that's a tad bit different.

Clarity is really a property of sentences, not propositions. If a sentence is unclear then it doesn't stand for any particular proposition, so it doesn't make a lot of sense to say the proposition it stands for is logically possible.

The concept of god is clear?

Something that had no beginning yet has existence.

Something allegedly at the center of things but something with the least evidence to support it's existence.

 

[fast]

I don't think clarity is a necessary condition for whether some proposition is logically possible. Knowledge of whether some proposition is logically possible (maybe), but that's a tad bit different.

Clarity is really a property of sentences, not propositions. If a sentence is unclear then it doesn't stand for any particular proposition, so it doesn't make a lot of sense to say the proposition it stands for is logically possible.

Same thing, then. If a sentence is unclear, then I don't KNOW if the proposition expressed is logically possible. Denial is unwarrented, since we cannot guarantee that it's logically possible or logically impossible. Now, if it's nonsense, then that's another issue entirely.

If God does not exist, then the term, "God" has no referent, but that has no bearing on whether the term has one or more meanings. What's so unclear about what the term means? If someone says, "people who believe in God believe they are praying to God when they pray," then is that all that unclear? If that's true, then it's possible. If that's false, it's still logically possible, even if we have different notions of God.

 

[Bomb#20]

Clarity is really a property of sentences, not propositions. If a sentence is unclear then it doesn't stand for any particular proposition, so it doesn't make a lot of sense to say the proposition it stands for is logically possible.

Same thing, then. If a sentence is unclear, then I don't KNOW if the proposition expressed is logically possible. Denial is unwarrented, since we cannot guarantee that it's logically possible or logically impossible. Now, if it's nonsense, then that's another issue entirely.

To say "the proposition expressed" is to presume it expresses some proposition. If a sentence is unclear then what reason is there to think it expresses any proposition at all?

If God does not exist, then the term, "God" has no referent, but that has no bearing on whether the term has one or more meanings. What's so unclear about what the term means? If someone says, "people who believe in God believe they are praying to God when they pray," then is that all that unclear? If that's true, then it's possible. If that's false, it's still logically possible, even if we have different notions of God.

It's not clear what they believe. Sure, they believe there exists some entity, and they're trying to send their prayers to it; but what property are they ascribing to that entity when they call it "God"?

Suppose a cop told a Christian "God heard your prayer. We have proof. Your neighbor's 14-year-old kid installed spyware all over the neighborhood, and she turns on people's computers remotely, and when we arrested her she was listening to a recording of your prayer. And she's so brilliant other hackers call her 'God'.". The Christian isn't going to say "I knew it! There is a God!". He's just going to say "Heh. Funny. Throw the book at her. Wait, never mind, I forgive her." So what criterion does the kid not satisfy, that makes the Christian rule her out as possibly being the entity he was praying to?

 

[Bomb#20]

That is merely an unsupported and unsupportable claim. In that regard it is nothing to take seriously.

Unsupported, certainly. Unsupportable? That's not obvious. How do we know what some brilliant future philosopher might figure out? Do you have proof that the hypothesis is unsupportable?

It is a claim about "every event".

Since it is impossible to examine "every event" it is an unsupportable claim.

We support claims about "every X" on a regular basis even when it's impossible to examine every X. Every uranium atom is unstable. Every animal is younger than 1000 years. Every bacterium is smaller than 1 gram. Every galaxy over a billion light-years away is red-shifted. Claims like those are supported by being implied by well-supported theories, or else by plain old scientific induction.

Could it possibly someday in the future be supportable? I doubt it, but nobody knows that. All we know for certain is that presently it is unsupportable.

Ah, by "unsupportable" you meant "presently unsupportable". Is that different from "unsupported"?

As for whether to take it seriously, that's a matter of taste. The world is overflowing with unsupported but logically possible hypotheses -- it's logically possible that there's a teacup orbiting Jupiter. Mere logical possibility is not a good reason to take a hypothesis seriously.

It is not logical to claim a teacup is orbiting Jupiter without evidence. That is not a matter of taste.

Nobody said otherwise; but nobody claimed a teacup is orbiting Jupiter. It's a hypothesis, not a claim. It's perfectly reasonable to take some hypotheses seriously even when nobody is claiming them. I have no evidence that my brother is going to die of cancer, but of course I take seriously the hypothesis that he will. I don't take seriously the hypothesis that he'll die by being struck by lightning. What it's reasonable to take seriously is a matter of probability estimates. We don't take the teacup scenario seriously because it's wildly improbable, not because it's impossible.

The point is, if you think the probability that every event had a prior event is less than, say, 1%, feel free to not take the hypothesis seriously. But unless one can justify them, probability estimates themselves are a matter of taste. Can you justify a claim that there's at least a 99% chance that there was a First Cause? Can you even justify your opinion that there's at least a 51% chance that there was a First Cause?

It is a matter of what can be supported with some kind of argument that makes sense or actual evidence.

How did the cup get there? If all you have is empty speculation and no evidence you do not have a logical possibility. You have a wild unsupported guess, not the same thing.

The cup got there by being either (a) accidentally left aboard the Galileo or Juno probe by some idiot at JPL, or (b) taken there by space aliens after they visited Earth. Empty speculation and no evidence is quite enough for logical possibility. We can tell empty speculation is enough for logical possibility, because empty speculation is all we have arguing for a universe with no beginning, and empty speculation is also all we have arguing for a First Cause, and one of them must be true. If "That's just empty speculation." were enough to refute eternity, it would also be enough to refute a beginning.

You might as well dump a bag of foam peanuts on the floor, announce that there are an even number of peanuts, and then try to refute anyone who says the number might be odd by saying "You have no evidence that there are an odd number. All you have is empty speculation. So you do not have a logical possibility. Therefore the number is even.".

You don't have to observe something to understand what it means. I understand what it means for Brutus to stab Caesar even though there's no place I could observe that phenomenon. What it means for something to go on without end is that every event is followed by more events. An event is either followed by another or it isn't, just as a point on Earth either has more points north of it or it does not.

You understand what it is for one human to stab another. You have no understanding of how Brutus stabbed Caesar. You don't know what weapon he used. You don't know how he used the weapon. You don't know where in his body he stabbed Caesar.

According to Suetonius the attackers used daggers. What of it? As you say, I understand what it is for one human to stab another. That's enough for the claim to be clear, because I made no claim about the lower-level details you bring up.

If you think understanding nothing about an event is actually understanding the event I can see your difficulty.

Who said I understood the event that had a subsequent event? Why would I have to understand an event itself in order to understand its temporal relationship to another event? You might as well claim that if you woke up in a hospital and a nurse told you you were a hit-and-run victim, you'd have to know the motivation of the driver to figure out it happened before you woke up in the hospital.

"Something to go on without end" are words. Not an understanding of anything.

Why, because you say so? I understand that if you say "There will be a last event.", and I say "Which event will that be?", and you point at your diagram of projected future history and say "That one.", then "go on without end" means you will be wrong.

What does it look like when something is going on without end? How do we recognize the phenomena?

What does it look like when something is going on with an end? How do we recognize the phenomenon? We don't. With or without end, the currently observable sequence of events would look the same. If that were an argument against no end, it would be an equally good argument against an end.

Or do some just look at a phenomena and claim it can go on without end without the least bit of evidence to support the wild claim?

Well, we already know for a fact that some just look at a phenomenon and claim it can't go on without end without the least bit of evidence to support the wild claim. What makes you feel your claim of knowledge requires less evidence than our agnosticism?

In other words an empty claim. As empty as a claim about how Brutus stabbed Caesar.

Why is a claim that Brutus stabbed Caesar with a dagger empty?

 

[ryan]

Is it logically possible that Jesus was the son of god?

Was it logically possible that the Big Bang was a miracle of some bored gods?

What does it mean for something to be logically possible? What are the objective criteria to determine such a thing?

How does logic make things possible?

Does logic or modeling off data, or actual data, show it is possible or impossible to move faster than the speed of light?

There is no logic in saying because there was a yesterday that means there may have been infinite yesterdays. No logic to saying because the past is a mental collection of present moments those present moments were possibly infinite.

How does some idea with no evidence to support it become logically possible?

Here is an example of using logic that may help us in the real world.

Think of some bridge with a maximum load weight of 1000 kg. We start with an axiom that the bridge holds a maximum of 1000 kg, and anything more will collapse the bridge.

A real world use for a simple - but crucially important - inductive <deductive> logic says that if I have a 1200 kg truck on the bridge, the total load will collapse the bridge.

If I were illogical, I would say that more than 1000 kg will not collapse the bridge and clearly I would be wrong. That is a contradiction with real world consequences.

Oops, I meant "deductive" not 'inductive".

Untermensche, do you see how something could be logically possible?

 

[untermensche]

Here is an example of using logic that may help us in the real world.

Think of some bridge with a maximum load weight of 1000 kg. We start with an axiom that the bridge holds a maximum of 1000 kg, and anything more will collapse the bridge.

A real world use for a simple - but crucially important - inductive <deductive> logic says that if I have a 1200 kg truck on the bridge, the total load will collapse the bridge.

If I were illogical, I would say that more than 1000 kg will not collapse the bridge and clearly I would be wrong. That is a contradiction with real world consequences.

Oops, I meant "deductive" not 'inductive".

Untermensche, do you see how something could be logically possible?

I would never claim that nothing is logically possible.

This is about the limits to what one can say is logically possible.

It is logically possible it will rain tomorrow.

It is not logically possible I will be infinite in some way tomorrow.

 

[untermensche]

We support claims about "every X" on a regular basis even when it's impossible to examine every X. Every uranium atom is unstable. Every animal is younger than 1000 years. Every bacterium is smaller than 1 gram. Every galaxy over a billion light-years away is red-shifted. Claims like those are supported by being implied by well-supported theories, or else by plain old scientific induction.

Can you say there are infinite atoms in the universe? Does that make any sense? The number is always growing somehow from somewhere?

Can we say there are infinite bacteria in the universe?

Infinite galaxies?

Sure, atoms have properties and we can be pretty sure but not absolutely certain that the properties define all potential behavior.

And we can't talk about every animal, or every bacteria in the universe.

You can't talk about galaxies not seen. But we assume the "laws" of the universe are the same everywhere in the universe. That is an assumption, not an established fact.

According to Suetonius the attackers used daggers.

In other words you don't know.

Humans lie all the time. Was Suetonius human?

 

[ryan]

Oops, I meant "deductive" not 'inductive".

Untermensche, do you see how something could be logically possible?

I would never claim that nothing is logically possible.

This is about the limits to what one can say is logically possible.

It is logically possible it will rain tomorrow.

It is not logically possible I will be infinite in some way tomorrow.

Then give a proof. You can't just give extreme examples where one case isn't true; you must give an argument where all cases of infinity, or at least cases like time or distance, must be false/impossible.

Give some reasonable postulates and see if you can prove your claim with them.

Will you try this?

 

[fromderinside]

Can you say there are infinite atoms in the universe? Does that make any sense? The number is always growing somehow from somewhere?

Logically it only needs to beyond counting by those who do such. That is infinite is logically possible by definition.

I'm confident that if every human who ever existed exclusively counted molecules in the universe at the highest rate humans can individually without aid of machines assess and count molecules one by one we would not have possibly counted all the molecules in the universe by the time we become extinct. What do you think of the caveats?

 

[ryan]

Can you say there are infinite atoms in the universe? Does that make any sense? The number is always growing somehow from somewhere?

Logically it only needs to beyond counting by those who do such. That is infinite is logically possible by definition.

This is about actual infinity, not apparent infinity.

 

[untermensche]

Can you say there are infinite atoms in the universe? Does that make any sense? The number is always growing somehow from somewhere?

Logically it only needs to beyond counting by those who do such. That is infinite is logically possible by definition.

I'm confident that if every human who ever existed exclusively counted molecules in the universe at the highest rate humans can individually without aid of machines assess and count molecules one by one we would not have possibly counted all the molecules in the universe by the time we become extinct. What do you think of the caveats?

An infinite number of humans who lived infinite years could not count infinite atoms.

Infinity is not something that can be counted. If something has no limit it can't be counted.

It is imaginary.

 

[Copernicus]

"Logical possibility" refers to a claim that is consistent with all the premises that one holds to be true (i.e. not contradicted by a premise) in a given model of the world. So a valid conclusion need not actually be true, just consistent with all the premises that are considered true. Since we can posit a great many models of reality that are inconsistent with each other, we normally hold any empirical claim to be logically possible, even though we don't necessarily accept the model that the claim is consistent with to be plausible. That is, implausible claims are logically possible. Inherently false claims are not empirical--e.g. "Red objects are colorless"--and therefore not logically possible.

 

[ryan]

"Logical possibility" refers to a claim that is consistent with all the premises that one holds to be true (i.e. not contradicted by a premise) in a given model of the world. So a valid conclusion need not actually be true, just consistent with all the premises that are considered true. Since we can posit a great many models of reality that are inconsistent with each other, we normally hold any empirical claim to be logically possible, even though we don't necessarily accept the model that the claim is consistent with to be plausible. That is, implausible claims are logically possible. Inherently false claims are not empirical--e.g. "Red objects are colorless"--and therefore not logically possible.

Excellent, perfect response to the OP.

Now all Unter has to do is provide some premises/postulates regarding the negative claim of infinity that are reasonable, and an actual philosophical argument can be made.

 

[untermensche]

I would never claim that nothing is logically possible.

This is about the limits to what one can say is logically possible.

It is logically possible it will rain tomorrow.

It is not logically possible I will be infinite in some way tomorrow.

Then give a proof. You can't just give extreme examples where one case isn't true; you must give an argument where all cases of infinity, or at least cases like time or distance, must be false/impossible.

Give some reasonable postulates and see if you can prove your claim with them.

Will you try this?

I don't have to prove imaginary things are imaginary.

It is entirely up to those who say something is real to demonstrate it.

Infinity is an imaginary concept.

Applying it to real entities is an absurdity.

 

[ryan]

Then give a proof. You can't just give extreme examples where one case isn't true; you must give an argument where all cases of infinity, or at least cases like time or distance, must be false/impossible.

Give some reasonable postulates and see if you can prove your claim with them.

Will you try this?

I don't have to prove imaginary things are imaginary.

It is entirely up to those who say something is real to demonstrate it.

Infinity is an imaginary concept.

Applying it to real entities is an absurdity.

Okay, but just saying it's so is not going to help your case.

Think of infinity as a quantity of something that we know already exists. If one apple exists, then it isn't a leap to think that 2 can exist. If 2 apples can exist, then ... The universe might max out with apples, but then again it might not - we don't know yet.

 

[untermensche]

I don't have to prove imaginary things are imaginary.

It is entirely up to those who say something is real to demonstrate it.

Infinity is an imaginary concept.

Applying it to real entities is an absurdity.

Okay, but just saying it's so is not going to help your case.

Think of infinity as a quantity of something that we know already exists. If one apple exists, then it isn't a leap to think that 2 can exist. If 2 apples can exist, then ... The universe might max out with apples, but then again it might not - we don't know yet.

Infinite apples would not fit in infinite universes.

 

[beero1000]

Okay, but just saying it's so is not going to help your case.

Think of infinity as a quantity of something that we know already exists. If one apple exists, then it isn't a leap to think that 2 can exist. If 2 apples can exist, then ... The universe might max out with apples, but then again it might not - we don't know yet.

Infinite apples would not fit in infinite universes.

What new idiocy is this?

 

[untermensche]

Infinite apples would not fit in infinite universes.

What new idiocy is this?

How much space would infinite apples occupy?

Please be specific.

The exact amount.

 

[Bomb#20]

Can you say there are infinite atoms in the universe?

I don't know if the number is finite or infinite. No human knows. Maybe some advanced space alien knows. But it's logically possible. Even if you're an advanced space alien and your people have made measurements of space-time curvature that imply the number is finite, that would only show infinite atoms are physically impossible, not logically impossible.

Does that make any sense? The number is always growing somehow from somewhere?

Well, if the number is always growing then it's finite. If it's infinite then adding new atoms doesn't make the number grow. Infinity plus one is still infinity.

Can we say there are infinite bacteria in the universe?

Define "bacteria". Is it a word like "mammal" that refers to a specific group of related organisms, or a word like "tree" that refers to a general physical type? There might perhaps be infinitely many trees; there are surely only finitely many mammals, since all mammals in the universe are descended from some original animal that lived on Earth 200ish million years ago.

Infinite galaxies?

Same answer as infinite atoms.

Sure, atoms have properties and we can be pretty sure but not absolutely certain that the properties define all potential behavior.

Right. Absolute certainty is hard to come by. We make claims about what's infinite the same way we make claims about what's radioactive: based on what follows from the most successful theories and the latest observations. Scientific claims are claims that something is probably true, not absolutely certain.

And we can't talk about every animal, or every bacteria in the universe.

You can't talk about galaxies not seen. But we assume the "laws" of the universe are the same everywhere in the universe. That is an assumption, not an established fact.

We talk about galaxies not seen all the time. Mostly that's just galaxies too faint or too far away to see. Sometimes it's about galaxies hidden by bigger galaxies that are in the way. Sometimes it's about galaxies outside our light-cone, theorized to exist because there's no theoretical reason for the universe to be a sphere with us in the exact center. And yes, much of what we infer about the universe is based on the assumption that the laws we've discovered are the same everywhere. Yes, it's an assumption, not an established fact. But then, the hypothesis that the laws are different in different parts of the universe isn't established fact either. The laws might be the same everywhere. It's logically possible that the laws are the same everywhere.

According to Suetonius the attackers used daggers.

In other words you don't know.

Humans lie all the time. Was Suetonius human?

Sure, he might have been lying. More likely, he might have been misinformed -- Suetonius wrote his book about 150 years after the fact. But he was Rome's imperial archivist; he had access to contemporary accounts; so he probably got his details mostly right. Caesar was stabbed 23 times. The killing blow took out his aorta and he died of blood loss, according to the autopsy (incidentally, the world's earliest autopsy we still have a record of.)

But none of that is the point. Even if we suppose Suetonius was lying or misinformed, we know what it means to say someone stuck a dagger into a guy's aorta and he bled out. Even if it's false, there's nothing unclear about the proposition, even though the event is no longer observable. The point is, an event doesn't have to be observable for a statement about that event to be clear and meaningful.