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Reductio ad Absurdum

reductio ad absurdum

(also known as: reduce to absurdity)

Description: A mode of argumentation or a form of argument in which a proposition is disproven by following its implications logically to an absurd conclusion.  Arguments that use universals such as, “always”, “never”, “everyone”, “nobody”, etc., are prone to being reduced to absurd conclusions.  The fallacy is in the argument that could be reduced to absurdity -- so in essence, reductio ad absurdum is a technique to expose the fallacy.

Logical Form:

Assume P is true.

From this assumption, deduce that Q is true.

Also, deduce that Q is false.

Thus, P implies both Q and not Q (a contradiction, which is necessarily false).

Therefore, P itself must be false.

Example #1:

I am going into surgery tomorrow so please pray for me.  If enough people pray for me, God will protect me from harm and see to it that I have a successful surgery and speedy recovery.

Explanation: We first assume the premise is true: if “enough” people prayed to God for the patient's successful surgery and speedy recovery, then God would make it so.  From this, we can deduce that God responds to popular opinion.  However, if God simply granted prayers based on popularity contests, that would be both unjust and absurd.  Since God cannot be unjust, then he cannot both respond to popularity and not respond to popularity, the claim is absurd, and thus false.

Example #2:

If everyone lived his or her life exactly like Jesus lived his life, the world would be a beautiful place!

Explanation: We first assume the premise is true: if everyone lived his or her life exactly like Jesus lived his, the world would be a beautiful place.  If this were true, we would have 7 billion people on this earth roaming from town to town, living off the charity of others, preaching about God (with nobody listening). Without anyone creating wealth, there would be nobody to get charity from -- there would just be 7 billion people all trying to tell each other about God.  After a few weeks, everyone would eventually starve and die.  This world might be a beautiful place for the vultures and maggots feeding on all the Jesus wannabes, but far from a beautiful world from a human perspective.  Since the world cannot be both a beautiful place and a horrible place, the proposition is false.

Exception: Be sure to see the appeal to extremes fallacy.

References:

Eemeren, F. H. van, Garssen, B., & Meuffels, B. (2009). Fallacies and Judgments of Reasonableness: Empirical Research Concerning the Pragma-Dialectical Discussion Rules. Springer Science & Business Media.



Registered User Comments

:P
Friday, May 25, 2018 - 11:57:29 AM
The only problem with the second example is that no money doesn't lead to death if every producer is willing to feed those non producers. If everyone lived like Jesus then there would not be any wealth is true. However this would then conclude that people would just live without wealth. The failure of Marxism wasn't due to people helping each other was wrong it was because people can be forced into altruism. Thus if everyone suddenly followed what Jesus would do, there would be no failure because by assumption no one would not follow altruistic behavior :) (btw the Gospels don;t say Jesus hates wealth it just says that he hates hoarding when the hoarders don't help those that need it)

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:P
Friday, May 25, 2018 - 12:13:23 PM
in summery if everyone was forced to be an altruist then the world would be a worse place, if everyone was an altruist then the would be a good place

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Bo Bennett, PhD
Friday, May 25, 2018 - 12:25:57 PM
But in the example, everyone is a non-producer hoping living off the charity of others. If "Jesus" is to religiously charged for you, substitute "Bob, the hobo from Los Angeles who tap dances for money." If Bob survives off the charity of those who have food and provide him with food, and Bob does not have any food of his own or produce any food, if everyone were like Bob, there would be no food—just a lot of tap dancers.

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:P
Wednesday, July 04, 2018 - 09:27:01 PM
@Bo Bennett, PhD: thats an overly literal fallacy beacuse no one means do the exact job of individual x when your suppose to be like x, it just mean to emulate their character traits. No christian has ever said it should be illegal to be a non-carpenter which is also a straw man. Its also absurd to think when Johnny said that I want to be like their dad one day, that Johnny meant he wanted to marry his mother.

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:P
Wednesday, July 04, 2018 - 09:28:51 PM
@Bo Bennett, PhD: Given your particular version of that argument however its perfectly fine to say its absurd to take it literal, however hopefully my other comment shows its absurd to take anyone literal in that context. :P

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:P
Wednesday, July 04, 2018 - 09:35:27 PM
@demetri.bazos: re: similar character traits not same LUL

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Bo Bennett, PhD
Thursday, July 05, 2018 - 09:33:15 AM
@demetri.bazos: You are calling fallacy on my examples purposely designed to be fallacies.

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:P
Friday, July 13, 2018 - 11:51:32 PM
thats fine. Sry to be condescending sounding but if at all possible could you go through were i went wrong

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Bo Bennett, PhD
Saturday, July 14, 2018 - 02:21:15 AM
@:P: This is a website about fallacies. Errors in reasoning. In order to demonstrate these fallacies I give examples. Some examples are common that one might see often, others are more exaggerated and quite rare in order to make the fallacy more clear. Every example is fallacious. If you say "nobody would say that," you might be right - but I am not claiming they would (strawman). Readers get emotional over the examples because they feel they make them look bad through association. I have taken heat from Christians, creationists, flat-earthers (they are the most nasty), atheists, liberals, conservatives, and even ghost hunters. My message to everyone - stop taking these examples personally unless you look at the example fallacy and say "that makes perfect sense to me... I see nothing wrong with that." Otherwise, we are in agreement.

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Electro_blob
Sunday, September 24, 2017 - 12:54:43 AM
This is a blatantly biased website against Christians. A general example would be much more appropriate. People come onto these websites to learn about argument, not to have a God bashing session.
Prayer is a general appeal to God, much like a letter to a Senator, which can be rejected or accepted. God will do what he sees fit. If your prayer fits in to His schedule, it will be done. Otherwise, God will carry out His will, not yours.
The obvious intention of the second example is to state that we should follow the principles demonstrated by Jesus's life, not that we should literally act exactly as he does. Love God with all your heart, mind, and soul. Love your neighbor as yourself. If everyone followed these principles, the world would be a better place. Of course, you can not love anyone if you are starved to death and expect others to provide the funds for your gifts to no one. Jesus would not preach to believers something they already know, he would only strengthen it. Nor would Jesus starve himself to death. Your assumptions are unrealistic. However, if everyone worshiped God, worked hard to improve their lives, and helped to improve other people's lives, the world would be perfect.
All your conclusions based on the proposed statement are valid, but the wording of the examples are obviously biased to lead your reader to believe that Christian arguments are generally invalid.

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Bo Bennett, PhD
Sunday, September 24, 2017 - 06:15:40 AM
If you make it past one example that offends you, you will find that I am an equal opportunity "basher," where I highlight bad arguments from Christians, Muslims, Atheists, Liberals, Conservatives, men, women, etc. My examples are of bad (fallacious) arguments—I don't care who makes them. You are committing a strawman in your defense of "living like Jesus." The argument is "If everyone lived his or her life exactly like Jesus lived his life," you are talking about "loving God and neighbors." By talking out the absurd conclusions of this scenario, we might ultimately get to the arguer rewording his argument to something such as "I meant if everyone follows Jesus' advice of loving God and loving your neighbor," then the argument would have advanced. This is the entire point of this strategy. If you want to avoid fallacies, shelve your emotion and defensiveness and approach the argument objectively.

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SamGreyson
Friday, November 10, 2017 - 10:19:37 AM
I agree with what you are saying sir. Glad you noticed this as well.

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tuqqer
Sunday, February 11, 2018 - 10:15:39 AM
"God will do what he sees fit."

Who told you that? And what made you decide to believe it? These aren't rhetorical questions.

"God will do what he sees fit" isn't a factual statement. It's a belief. Forget whether it's a good or bad belief, I personally think it's fine as beliefs go. But this is a logical fallacy site. It's just important to realize that what you're saying is a belief. Not a factual statement.

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Nick McGivney
Wednesday, May 17, 2017 - 06:48:42 PM
First time I ever got so much more bang than buck when searching a simple definition. I commend the material, and I commend the writer for adding so much more to it through their beautifully wrought examples. I am pure entertained.

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Dave W
Saturday, August 05, 2017 - 02:03:13 PM
Huh. You must be used to raw deals, indeed! But I see what you mean about the entertainment. It is always enjoyable watching fools present themselves as wise men. What else is the internet for?

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Dave W
Saturday, August 05, 2017 - 02:00:34 PM
Ok. Very enlightening. But you should have added another fallacy: The Straw Man Fallacy. Anyone desiring two good examples need look no further than those given above about prayer and Christ-likeness. A more impressive use of your time would be seeing how many Christians you could find who would actually explain their understanding of prayer or Christ-likeness in the terms given above. I'll save you some time: You would find none. A child of 8 raised in a mature Christian home could easily distinguish between the nonsense above and the actual beliefs of Christianity. No, 6. No, 5. Maybe younger. But friend, I sympathize with you. I am well acquainted with the miserable task of the anti-Christian who makes the mistake of taking on an educated Christian in debate. Much, much safer to offer the most childish interpretation of Christianity imaginable and then attack that. You would have no hope against the Real Thing.

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