Reductio ad absurdum

[Jamie123]

I used to take the position that it was not possible to know whether or not the Book of Mormon was true, until the following arguments struck me:

First argument: If it's impossible to know whether or not it's true then:

1. I cannot know whether or not it's true, and therefore...

2. I must accept the possibility that it is true, and...

3. I must also accept the possibility that Moroni's promise is true, and...

4. I must therefore accept the possiblity that it is possible to know that it is true.

Which contradicts my original assumption.

Second argument: If it's impossible to know whether or not it's true then:

1. Moroni's promise must be false, and...

2. Therefore the Book of Mormon is false, and....

3. It is therefore possible to know that it is false.

Which again contradicts the first assumption.

Conclusion: Even if we haven't yet found a viable means of knowing whether or not the Book of Mormon is true, we can't deny the possibility that it is possible to know one way or the other.

Opinions welcome :)

[FunkyTown]

Number 3 of the first argument is a non-sequitur.

Just because the Book of Mormon is 'true'(Depending on what you mean by 'true') doesn't mean Moroni's promise has to be true. Moroni could have been lying, mistaken or crazy. Simply put: Just because the Book of Mormon was written by the people it says it is, even if you assume they believe what they wrote, it doesn't necessarily follow that what they wrote is objectively correct.

Also, number 3 of the second argument is another non-sequitur. If(For the sake of this argument), Moroni's words are untrue, it doesn't follow that we would know them to be untrue. I will give an example:

There are sixty-three billion, nine hundred and ninety-eight million, six-hundred and seventy-eight thousand, three hundred and six apples in the world.

If you pray about this number, you know it is true.

There are too many apples around the world in too many disparate places to count the exact number. Therefor, it is impossible to know if the number I gave was correct.

If I was false when I spoke and said you could know the number of apples in the world via prayer, it doesn't follow that you would know that it was false when I spoke it.

[Jamie123]

Thanks for the comments FunkyTown :) If I might respond....

Just because the Book of Mormon is 'true'(Depending on what you mean by 'true') doesn't mean Moroni's promise has to be true. Moroni could have been lying, mistaken or crazy.

If he were lying, mistaken or crazy, his words might still appear in a "true" book as reported speech, but they don't: they appear as the final (or almost final) words of the author. In any case, I didn't say Moroni's promise had to be true. I said I would have to accept the possibility that it is true.

If(For the sake of this argument), Moroni's words are untrue, it doesn't follow that we would know them to be untrue.

You miss the point here: I am assuming that it is impossible to know whether or not the Book of Mormon is true. Moroni on the other hand promises that it is possible. If my assumption is correct then Moroni's promise is false, which in turn undermines the "trueness" of the entire book. Since I can draw this conclusion, my original assumption must be incorrect.

Edited June 22, 2012 by Jamie123

[FunkyTown]

You miss the point here: I am assuming that it is impossible to know whether or not the Book of Mormon is true. Moroni on the other hand promises that it is possible. If my assumption is correct then Moroni's promise is false, which in turn undermines the "trueness" of the entire book. Since I can draw this conclusion, my original assumption must be incorrect.

That's assuming a third person omniscient point of view from Moroni. Moroni was not Omniscient. In the same sense that I could promise that you could pray to know the perfect recipe rabbit stew at the end of any cookbook I made wouldn't invalidate the rest of the cookbook, Moroni and his promise don't have to be true in order for the book to be a historical document.

Note that I do think Moroni's promise is true. I just think the logical argument that we can necessarily know that fact is false based on how it's been presented.

[Jamie123]

Moroni and his promise don't have to be true in order for the book to be a historical document.

If that's what you mean by "true" then you could call the Iliad, the Volsunga Saga, the Mahabharata and Journey to the West "true books" in the sense that they report real historical happenings (along with dragons, warring goddesses and monkeys with magic chest-hairs).

That's not the kind of "trueness" I'm talking about. If the book is "true" in the sense that the missionaries make it out to be, then the words of the authors need to be reliable.

Edited June 22, 2012 by Jamie123
Worded it a bit better.

[FunkyTown]

If that's what you mean by "true" then you could call the Iliad, the Volsunga Saga, the Mahabharata and Journey to the West "true books" in the sense that they report real historical happenings (along with dragons, warring goddesses and monkeys with magic chest-hairs). I assumed Moroni's promised more by "...God shall show unto you, that that which I have written is true" than that some of the events in the book really happened.

That becomes a circular argument, Jamie. If you're saying:

"I believe the definition of whether this book is true or not comes down to Moroni's promise."

"Moroni's promise is that you can know if the book is true."

"If the book is true, then Moroni's promise is true."

That's circular and essentially a meaningless argument in logic.

If Moroni is correct, then you can know if it's true. If Moroni is incorrect, then you can't. It's really that simple.

[Jamie123]

If Moroni is correct, then you can know if it's true. If Moroni is incorrect, then you can't. It's really that simple.

With all due respect FunkyTown, no it's not: This statement would only be valid if Moroni's promise were external to the Book of Mormon. If I were to accept that Moroni's promise were false then I would also have to accept that the Book of Mormon was false (since it contains Moroni's promise) and I would therefore no longer be in a state of indecision about the book's truth.

Edited June 22, 2012 by Jamie123
spelling

[FunkyTown]

With all due respect FunkyTown, no it's not: This statement would only be valid if Moroni's promise were external to the Book of Mormon. If I were to accept that Moroni's promise were false then I would also have to accept that the Book of Mormon was false (since it contains Moroni's promise) and I would therefore no longer be in a state of indecision about the book's truth.

Okay. Let's go with that:

This would be true only if you knew it to be false. If you didn't, then you still wouldn't be able to know if it were true or false.

[Jamie123]

Note that I do think Moroni's promise is true. I just think the logical argument that we can necessarily know that fact is false based on how it's been presented.

My apologies: I missed this point first time around. I'm not suggesting here that we can necessarily know either way. My argument is that the statement: "we cannot possibly know" is logically untenable.

[Jamie123]

This would be true only if you knew it to be false. If you didn't, then you still wouldn't be able to know if it were true or false.

LOL - I think we're finally in agreement :)

[Jamie123]

This would be true only if you knew it to be false.

Exactly: I'm not attempting to draw conclusions about the truth/faslehood of the BoM. I'm merely exploring the consequences of assumptions, like in the classic proof that the square root of 2 is irrational. (If we assume that sqrt(2)=p/q where p and q have no common factors, then it's easy to prove that p and q are both divisible by 2, which contradicts our initial assumption. Conclusion: sqrt(2) is irrational.)

If you didn't, then you still wouldn't be able to know if it were true or false.

I agree you may not in your current state of knowledge be able to know, but you couldn't claim that the question was irresolvable. That was the point I was making.

Edited June 22, 2012 by Jamie123

[Vort]

I used to take the position that it was not possible to know whether or not the Book of Mormon was true, until the following arguments struck me:

First argument: If it's impossible to know whether or not it's true then:

1. I cannot know whether or not it's true, and therefore...

2. I must accept the possibility that it is true, and...

3. I must also accept the possibility that Moroni's promise is true, and...

4. I must therefore accept the possiblity that it is possible to know that it is true.

Which contradicts my original assumption.

Second argument: If it's impossible to know whether or not it's true then:

1. Moroni's promise must be false, and...

2. Therefore the Book of Mormon is false, and....

3. It is therefore possible to know that it is false.

Which again contradicts the first assumption.

Conclusion: Even if we haven't yet found a viable means of knowing whether or not the Book of Mormon is true, we can't deny the possibility that it is possible to know one way or the other.

Opinions welcome :)

Very elegant.

[mnn727]

Opinions welcome :)

My opinion: Someone has too much time on their hands

[MarginOfError]

I used to take the position that it was not possible to know whether or not the Book of Mormon was true, until the following arguments struck me:

First argument: If it's impossible to know whether or not it's true then:

1. I cannot know whether or not it's true, and therefore...

2. I must accept the possibility that it is true, and...

3. I must also accept the possibility that Moroni's promise is true, and...

4. I must therefore accept the possiblity that it is possible to know that it is true.

Which contradicts my original assumption.

Second argument: If it's impossible to know whether or not it's true then:

1. Moroni's promise must be false, and...

2. Therefore the Book of Mormon is false, and....

3. It is therefore possible to know that it is false.

Which again contradicts the first assumption.

Conclusion: Even if we haven't yet found a viable means of knowing whether or not the Book of Mormon is true, we can't deny the possibility that it is possible to know one way or the other.

Opinions welcome :)

There's a conceptual flaw in the use of your logic. In your first argument, you assume that if the Book of Mormon is true, then Moroni's promise is true. Using a basic truth table, we can show that this is not necessarily true, and the argument unravels.

In the second argument, you assume that if Moroni's promise is true, the the Book of Mormon is true. Again, using a basic truth table, we can unravel the argument.

P Q P => Q

T T T

T F F

F T T

F F T

Notice that you conclusion can be true even when based on a false assumption, which is logically inadmissible.

By making both arguments, you've made the Book of Mormon a necessary and sufficient condition for Moroni's promise. This is necessary for your argument to succeed

To put this in logical terminology,

Let P = The Book of Mormon is true

Let Q = Moroni's promise is true

Let P <=> = The Book of Mormon is true if and only if Moroni's promise is true

Consider the following truth table

P Q P <=> Q

T T T

T F F

F T F

F F T

However, it isn't clear that this is actually true. Specifically because Moroni's promise could be true (it is possible to know), but the Book of Mormon could be false. But your explanation would have to objectively reconcile the event that two independent people follow Moroni's counsel, each pray to know if it is true, and one learns that it is true and one learns that it is false. Until you can objectively defend the biconditional P <=> Q, your argument cannot be a valid proof.

[Vort]

However, it isn't clear that this is actually true. Specifically because Moroni's promise could be true (it is possible to know), but the Book of Mormon could be false.

Not so. Moroni's promise is that the Lord will manifest the truthfulness of the Book of Mormon. If the Book of Mormon is false, Moroni's promise is neither true nor false, but undefined.

[MarginOfError]

Not so. Moroni's promise is that the Lord will manifest the truthfulness of the Book of Mormon. If the Book of Mormon is false, Moroni's promise is neither true nor false, but undefined.

Even under that condition, the original argument can't be valid with an undefined assumption.

[Vort]

Even under that condition, the original argument can't be valid with an undefined assumption.

Only for the special form of the second argument. The first argument is a more general form, and does not depend on Moroni's promise being definable.

[Jamie123]

My opinion: Someone has too much time on their hands

LOL - if only 'twere true!