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Friday, July 31, 2015

Logic Laws and Flaws



Christian thinkers yield and appeal to logic because it reflects God’s orderly nature. The apostle Paul, making his defense in chains before a Roman governor and a Jewish king, said, "I am not mad, most noble Festus, but speak words of truth and reason. For the king, before whom I also speak freely, knows these things; for I am convinced that none of these things escapes his attention, since this thing was not done in a corner" (Acts 26:25-26).

Logic has basically 3 laws that are foundational to all reason and thinking:


1.   The Law of Identity: A is A.  
  
Example: God is God, not something else.



2.   The Law of Non-Contradiction: A is not non-A.  
   Example: God cannot be both personal and impersonal.



3.   The Law of the Excluded Middle: Either A or non-A.
  
Example: God either exists or does not exist. There is no other alternative.

The basic laws of logic are neither arbitrary inventions of God, nor principles that exist completely outside God’s being. They are not exactly like the laws of nature. God may violate the latter (say, suspend gravity), but He cannot violate the former because those laws are rooted in God’s own nature. Indeed, some scholars think the beginning of John’s Gospel, “In the beginning was the Word (Greek, logos)” is accurately translated, “In the beginning was Logic (a divine, rational mind).” For example, even God cannot exist and not exist at the same time, and even God cannot validly believe that red is both a color and not a color. When people say that God need not behave “logically,” they are using the term in a loose sense to mean “the sensible thing from my point of view.” Often God does not act in ways that people understand or would do in the same circumstances. But God never behaves illogically in the proper sense. He does not violate in His being or thoughts the fundamental laws of logic.

Summary of Logical Fallacies (Logic Flaws)  

1. Argumentum ad hominem = argument directed at a person rather than the idea being discussed: “How can anyone take Ronald Reagan seriously as a president? He was an actor!” It is foolish to evaluate any leader, past or present,  based only on a past occupation. (Other factors need to be considered, such as character and other past experiences.)

2. Argumentum ad ignorantiam = argument to ignorance or lack of proof so far: “Lots of people have taken this drug and it has not hurt them!” Are you sure about that? 

3. Argumentum ad logicam = argument to so-called logic or invalid proof: “Lots of people have taken this drug and the drug manufacturer’s study proves it is perfectly safe,” neglecting to mention that the manufacturer is naturally biased in its own favor and did not conduct its study in an objective way, such as a double-blind study. Sound evidence from an impartial source is needed. 

4. Argumentum ad misericordiam = argument or appeal to pity only, ignoring other relevant facts: “We must outlaw hunting so animals will not suffer!” What about hunters and their families suffering from hunger? 

5. Argumentum ad nauseam = argument to the point of nausea by repetition: People who keep repeating, “But children need their milk!” every time they hear of even a grown child who does not drink milk regularly, no matter what you say—whether lactose intolerance or excessive calories or protein is an issue. Of course, it is not a fallacy to state the truth again and again; what is wrong is to expect repetition alone to substitute for real arguments. 

6. Argumentum ad numerum = argument or appeal to numbers only: “This has to be right because so many people are doing it!” Oh really? Were the Nazis right because so many people voted for them? 

7. Argumentum ad populum = argument or appeal to the public or a certain group: “The coolest people like this so it must be good!” What does cool really mean, who defines it, and who made them God? 

8. Argumentum ad verecundiam = argument or appeal to unsuitable authority: “Socialism must be the best form of government because Albert Einstein said so!” Einstein was an authority on physics, not politics, but pride can tempt any authority figure to pontificate beyond what he or she should, and foolish hero worship can tempt the public to try to demand that their authorities pontificate like that. 

9. Broken Window fallacy = the fallacy that breaking windows, waging war, and other destructive acts benefit society by providing jobs for people repairing windows, making weapons, patching up war wounds and the like. But who wants to be the one having their window broken, their relatives slaughtered, or walking around with a prosthetic limbif able to walk at all? Such a society would be parasitic and could not exist for long without producing something good worth producing. Going back to that broken window, the store owner who replaces it now is back to where he or she started before the vandalism. The money he could have spent on something to benefit the economy is now lost for that purpose.

10. Circulus in demonstrando (circular reasoning)/ Petitio principii (begging the question): “I have a right to say what I want so you should not try to silence me.”  Here is the question begging to be proved rather than merely asserted:  Is having a right to X the same as other people having an obligation to allow you to have X? That is like saying X is true because X is true, but not saying why it is true. 

11. Complex question = a loaded question with a built-in assumption: A question like, “Have you stopped beating your cat?” is valid only if the thing presumed true (cat beating) has been established. 

12. Cum hoc ergo propter hoc = “with this, therefore that follows”/mistaking correlation for causation: "President Clinton had great economic policies; just look at how well the economy did when he was in office!" Perhaps that was because of the policies of the president before him. More proof is needed. 

13. Dicto simpliciter = “simple statement”/Sweeping generalization/Stereotyping: “Teenagers are younger than adults and therefore do not have the maturity to make important decisions.”  Teenagers are younger than adults by definition, but that does not mean they are incapable of making important decisions.  The biblical examples of Joseph, Daniel, and Mary the mother of Jesus show that they can. 

14. Equivocation = “to call by the same name” or to use a word that has different meanings but gloss over which meaning is intended: “Women have no need to be afraid of man-eating sharks!” Yes, they do since “man” in that sentence means humans, not just males. C.S. Lewis in The Problem of Pain gives a serious example of the equivocation fallacy:  “‘If God were good, He would wish to make His creatures perfectly happy, and if God were almighty He would be able to do what He wished. But the creatures are not happy. Therefore God lacks either the goodness, or power, or both.’  This is the problem of pain, in its simplest form. The possibility of answering it depends on showing that the terms ‘good’ and ‘almighty’, and perhaps also the term ‘happy’, are equivocal.”  

15. False Analogy = inappropriate word picture or illustration: "What is the big deal about the early American pioneers killing a few natives to settle the West? After all, you cannot make an omelet without breaking a few eggs." Making an omelet has nothing to do with killing and stealing.

16. False Dilemma =  making an either/or statement when there are other options: "Either you buy a large car and watch it guzzle away your paycheck, or you buy a small car and risk being killed in an accident." Take the time to think through how many and what your options truly are.

17. Naturalistic fallacy = assuming nature or whatever is natural is always morally good; trying to bridge the is-ought gap: “Because many species of animals have multiple mates, so should we humans!” Just because, in a fallen world, some species do does not mean that humans ought to, especially since our Creator has clearly told us to be faithful for life to one’s husband or wife.  

18. Non sequitur = “it does not follow”/missing steps in the chain of reason: "Thousands of people have seen lights in the night sky that they could not identify. The existence of life on other planets is fast becoming certainty!" The second sentence needs more proof than what the first sentence states. 

19. Post hoc ergo propter hoc = “after this, therefore that follows”/assuming A led to B because A happened first: “The Patriots always win when I put on my lucky red shirt before they play!” Twice in 10 years maybe? 

Cleverly Avoiding Dangerous People!
20. Red herring = introducing emotional facts to distract from the issue at hand; a diversion: "It is claimed that welfare dependency leads to higher crime rates, but how are poor people supposed to keep a roof over their heads without our help?" It is important to help poor people with the necessities of life, but that does not refute the claim that welfare leads to crime. Not all red herrings are bad, however. Notice the red herring that rescued the apostle Paul from evil men who intended to kill him: “When Paul perceived that one part were Sadducees and the other Pharisees, he cried out before the Sanhedrin, ‘Men and Brothers, I am a Pharisee, the son of a Pharisee; concerning the hope and resurrection of the dead I am being judged!’ When he said this, an argument arose between the Pharisees and the Sadducees, and the assembly was divided. For Sadducees say that there is no resurrection—and no angel or spirit, but the Pharisees confess both” (Acts 23:6-8). Paul at that point was taken away by the Romans into protective custody. 

21. Slanting = saying something that is true, but in a misleading way for emotional effect: "The government keeps pouring money into the defense industry" or "The government naturally spends some money on the defense industry." The first sounds extravagant and wasteful; the second sounds minimal. Precise language and numbers are required to make an intelligent evaluation of the issue at hand.

22. Slippery slope = saying one thing inevitably leads to another when it does not (but sometimes it does):  A funny example of the slippery-slope fallacy is in the classic musical Music Man, where a con man tries to unload a bunch of musical instruments on an unsuspecting town by asserting, “Trouble, oh we got trouble, right here in River City!  With a capital T, that rhymes with P, and that stands for Pool (as in pool tables).  We gotta figure a way to keep the young ones moral after school!”  He cons the morality-conscious town into believing the only way to keep their teenagers from wasting their time on gaming after school is to get them all into a marching band! A serious but valid example of a slippery slope is how allowing one group of people to be treated in an inhumane way leads to inhumanity and suffering on a large scale. Think about these famous words from a repentant German pastor: “First the Nazis came for the Socialists, but I did not speak out because I was not a Socialist. Then they came for the Trade Unionists, but I did not speak out because I was not a Trade Unionist. Then they came for the Jews, but I did not speak out because I was not a Jew. And then they came for me, but there was no one left to speak for me.” (Martin Niemoller spent 8 years in Nazi concentration camps.) 

23. Straw man = fallacy of presenting an extreme version of someone’s point rather than the actual point: “Those Christians think Jesus is the only way, so they think the rest of us are wrong about everything!” Christians believe Jesus is the only way of salvation from sin because He said so and proved His claim in many ways, especially by rising from the dead. The Gospel is the Good News of God’s victory through Jesus Christ over Satan, sin, and death on behalf of His people. That should be the central issue of any Christian’s discussion with a non-Christian about Christ’s exclusivity. C.S. Lewis wrote in Mere Christianity, “If you are a Christian you do not have to believe that all the other religions are simply wrong all through.... When I was an atheist, I had to try to persuade myself that most of the human race have always been wrong about the question that mattered to them most; when I became a Christian I was able to take a more liberal view. But, of course, being a Christian does mean thinking that where Christianity differs from other religions, Christianity is right and they are wrong. As in arithmetic, there is only one right answer to a sum, and all other answers are wrong, but some...are... nearer being right than others.” Be sure to represent issues accurately, and expect others to as well. 

24. Tu quoque = “you too”/excusing your flawed logic because you accuse your opponent of using the same flaw: “Christians accuse us evolutionists of making unjustified assertions, but they assert a lot of things, too!” An error is still an error, regardless of how many people make it or merely are accused of making it.

Logic is an essential tool for the Christian to “speak the truth in love” (Ephesians 4:15) in a humble, respectful way (1 Peter 3:15).

PS. Teachers, it is very easy to make a quiz based on this material to test your students. Try multiple choice,  fill in the blank, true/false, essay, or any combination thereof!


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