Logic Experts Please!

[fluffybunny]

I've been through 9 books on logic and thought I had a good grasp on it, but while studying Tu Quoque with my son, he asks, very innocently, if the biblical saying: "take the log out of your own eye before taking the speck out of your own" is also Tu Quoque. :confused: This has stumped me. There must be a difference. I know I have heard the "log" accusation hurled at people who make an argument, in order to shut them up, but have never been able to put my finger on when there is a legitimate use.

 

Wikipedia writes it like this:

A makes argument P

A is also guilty of P

Therefore, P is dismissed

 

So,

 

The Pharisees (A) argue that a woman should be stoned for adultery as it is the law (P).

Jesus says the Pharisees (A) also commit sins (P).

Therefore, their argument (P), that she should be stoned, is invalid.

 

How is this not Tu Quoque? :001_huh:

[Deniseibase]

It is, in fact, logically invalid, presuming you accept the initial premise that those who are adulterers should be stoned. But very little in life operates on pure logic. Jesus is making a statement about sin and forgiveness, not logic.

 

You can, if you want to for the sake of argument, make this valid by saying there is an additional hidden premise that states that only someone with no sin can cast the first stone. But in order to do that, you have to say Jesus is not making a conclusion himself here but simply drawing out a hidden premise. Which makes the conclusion be that this woman should not be stoned and gives you this syllogism, with parentheses to indicate the hidden portion of the premise.

 

If this woman is an adulterer, then she should be stoned (if and only if someone can be found who had no sin).

She is an adulterer.

No one can be found who has no sin.

Therefore, this woman should not be stoned.

 

Hope that helps! Personally, as a former English major, I hope you don't try to add a hidden premise to the argument and just explain to your son that not every good thing in life is logically valid. It will be a sad day for the world if we ever have to make all our decisions based on logical validity :)

[fluffybunny]

Thank you Denise. Saying that not everything in life is dealt with by logic, or turning it into a syllogism, would not really answer my son's question .... nor mine. When can you legitimately say to someone: "take the log out of your own eye first, before telling me I'm X or Y."?

The question is still driving me nuts!

 

Does anyone know of any expert I could contact? I tried James Nance, but he doesn't reply. Doug Wilson has no contact; tried that. Martin Cothran; no contact found.

Edited April 4, 2012 by fluffybunny

[Classical Katharine]

I think it's interesting that Jesus wasn't addressing when we can tell the other guy to deal w/ his issues before we'll deal with ours. He was telling us to deal with ours before we deal w/ the other guy's. I was thinking about this recently . . . the fact that he says to all of us that we have a plank and the other guy has a speck. Aren't there some issues where the other guy has the plank and we have the speck? Well, I guess once we deal w/ our plank, there may be, but what I took from what Jesus said was that we have issues that are much bigger than we realize. He sees them, and we don't, and knowing that will change the way we deal with others' real issues. That we s/ always deal w/ others sins, if they must be addressed, knowing how great our own are in Jesus' eyes. Much easier to say than to do . . .

 

One of my pastors says we should be willing to learn about ourselves from anyone . . . so if even the guy w/ the plank in his eye comes to deal w/ my speck, I s/ still be willing to deal w/ my speck. Maybe the plank guy doesn't deserve to be listened to, maybe his conduct doesn't give him overall credibility, so maybe I don't automatically credit what he says b/c as I would if he were godly and reliable, but if he's right about my speck he's right about my speck. As for his plank, I need to pray for him and maybe seek to help him, but--ouch--not as a condition of dealing w/ my speck. My speck is mine to address no matter, ouch, what he does.

 

Jesus' standard is so high!

 

I don't know if this is exactly on your question. However I recall, and maybe this is related, that in my husband's logic textbook he deals with the appeal to authority, which some call a fallacy, and he says it is not a fallacy; it depends on whether the authority is indeed a relevant authority. So there is room for disagreement about the reach of certain identified fallacies or invalid ways of thinking (in layman's terms--I'm a layman), as to whether they are always uncalled for, or just usually.

[Iucounu]

The Biblical quote is dealing with hypocrisy, but it's not an example of tu quoque. Otherwise, we'd have to accept that Jesus was making an ad hominem attack in order to discredit an opponent's position during a logical argument, when he was really just teaching a religious lesson about moral values.

[Classical Katharine]

I expect this isn't definitive either but I found it interesting. It's from a not-fully-fleshed out section in Wikipedia (for better or for worse).

 

"The legitimate form of the argument is as follows:

A makes criticism P.A is also guilty of P.Therefore, A is dismissed (from his/her role as a model of the principle that motivates criticism P). The difference from the illegitimate form is that the latter would try to dismiss P along with A. It is illegitimate to conflate the logically separate questions of whether P is a valid criticism and whether A is a good role model.

Examples of legitimate use:

 

 

• In disqualifying a self-appointed judge. 'He can indeed accuse me of libel even though he was just successfully sued for libel, but perhaps he shouldn't.' "
  

 

Sounds sensible to me.

 

 

Also I think one thing that might be relevant to the OP's question is that Jesus wasn't telling people they had no right to accuse him because they are guilty themselves. He was telling people how to behave to one another. He wasn't trying to get or gain anything for himself, or prevent or preclude anything directed towards him.

[fluffybunny]

Thank you for your replies everyone. I can tell that everyone else is struggling with this one as well! Kathrine, I think that everyone has 'specks' in their eyes, as we're all just human and no one is perfect in this life. We can't beat ourselves up for lack of perfection! :-)

 

I did get a great reply from Martin Cothran (of Traditional Logic I and II which I have read), and the "go between the horns" technique has generally answered it for me. Jesus was confronted by a "dilemma". There are 3 ways to attack a dilemma, and "between the horns" is one way. This is what he said:

_________________________________

The purpose of a Tu Quoque argument is to discredit an opponent's position by pointing out that he does not act in accordance with it himself. If Person A says, "I think everyone should be a vegetarian," and Person B, in order to disprove the Person A's assertion, says "But you eat meat, don't you?", that is a Tu Quoque argument.

 

Jesus' admonitions in these two cases are not attempts to say that adultery is okay, or that the condemnation of sin in general is wrong. He is not impugning his interlocutor's positions about adultery or sin, therefore, it is not a Tu Quoque.

 

In the first case (of adultery) he is using a technique for short-circuiting a logical dilemma called "slipping between the horns." In the second, he is simply cautioning someone about the dangers of committing hypocrisy.

 

Does that make sense?

 

Martin

Edited April 7, 2012 by fluffybunny

[boscopup]

I've been through 9 books on logic and thought I had a good grasp on it, but while studying Tu Quoque with my son, he asks, very innocently, if the biblical saying: "take the log out of your own eye before taking the speck out of your own" is also Tu Quoque.

 

 

I don't know anything about Tu Quoque (my kids aren't logic stage yet), but I wanted to comment on the Biblical scenario here...

 

The Pharisees (A) argue that a woman should be stoned for adultery as it is the law (P).

Jesus says the Pharisees (A) also commit sins (P).

Therefore, their argument (P), that she should be stoned, is invalid.

 

This isn't quite what was happening. The law said the man AND the woman were to be stoned for adultery (Deut. 22:22, Lev. 20:10). These people had only brought the woman. The people were sinning in this process, saying she was guilty of breaking the law, when they themselves were breaking the law in bringing her alone to be stoned.

 

I don't believe Jesus is saying only people that don't sin in general are to cast the first stone. He's saying that only people who have not sinned in this particular act of accusing the woman should cast the first stone. He's pointing out their hypocrisy, in that the woman broke the law, but the accusers ALSO broke the law by not carrying out the punishment correctly.

 

The speck vs. plank issue is a different passage, and it's one filled with hyperbole. Again, it's dealing with hypocrisy, but not meaning that you can't point out someone's sins while you are doing some other sin. Everyone sins. That wouldn't even make sense. You are to judge with righteous judgement. But if I came up to you and condemned you for stealing a candybar when I just got done robbing a bank, I'd need to remove the plank from my own eye before pointing out the speck in yours. ;)